California: Individual County Chronologies
California Atlas of Historical County Boundaries
John H. Long, Editor; Peggy Tuck Sinko,
Historical Compiler; Laura Rico-Beck, GIS Specialist and Digital Compiler; Peter Siczewicz,
ArcIMS Interactive Map Designer; Emily Kelley, Research Associate; Robert Will, Cartographic Assistant
Copyright The Newberry Library 2003
25 Mar 1853 ALAMEDA created from CONTRA COSTA and SANTA CLARA. (Calif. Stats. 1853, 4th sess., ch. 41/pp. 56–59)
30 Mar 1874 ALAMEDA gained small area in San Francisco Bay from SAN FRANCISCO; placed all of the Central Pacific Railroad Wharf in ALAMEDA. The wharf was removed in 1919 [for location see 1874_pt.shp; change too small to display on interactive map]. (Calif. Stats. 1873, 20th sess., Acts Amendatory of the Codes, pp. 168–170; Coy, 62–63)
14 Mar 1878 Boundary between ALAMEDA and SAN MATEO in San Francisco Bay was adjusted [not mapped]. (Calif. Stats. 1877, 22d sess., Acts Amendatory of the Political Code, ch. 197/p. 71)
14 Jan 1958 ALAMEDA gained small area from CONTRA COSTA [for location see 1958_pt.shp; change too small to display on interactive map]. (Coy, 338–339)
02 Nov 1971 ALAMEDA lost small areas to SANTA CLARA [for location see 1971_pt.shp; change too small to display on interactive map]. (Coy, 338, 343)
01 Sep 1992 ALAMEDA gained small area from CONTRA COSTA. Ordinance passed 11 August 1992; effective 1 September 1992 [for location see 1992_pt.shp; change too small to display on interactive map]. (Minutes of the Board of Supervisors, Alameda County, 11 August 1992, ordinance 92–57)
11 Oct 1993 ALAMEDA boundaries restated to incorporate 1 September 1992 change [no change]. (Calif. Stats. 1993–1994, reg. sess., ch. 1195, sec. 2.5/p. 6853)
04 Oct 1995 ALAMEDA lost small area to CONTRA COSTA [for location see 1995_pt.shp; change too small to display on interactive map]. (Calif. Stats. 1995, reg. sess., ch. 529, sec. 3 in Official California Legislative Information, http://www.leginfo.ca.gov/statute.html, 23 September 2002)
19 Aug 1996 ALAMEDA boundary clarified [no discernible change]. (Calif. Stats. 1996, reg. sess., ch. 400, sec. 4 in Official California Legislative Information, http://www.leginfo.ca.gov/statute.html, 23 September 2002)
16 Mar 1864 ALPINE created from AMADOR, CALAVERAS, EL DORADO, MONO, and TUOLUMNE. (Calif. Stats. 1863–1864, 15th sess., ch. 180/pp. 178–182)
17 Nov 1995 ALPINE gained small area from AMADOR. Ordinance passed 3 October 1995; effective 17 November 1995 [for location see 1995_pt.shp; change too small to display on interactive map]. (Minutes of the Board of Supervisors, Amador County, 3 October 1995, ordinance 1390)
14 Jun 1854 AMADOR created from CALAVERAS. Act passed 11 May 1854; referendum for or against creation of the new county held 14 June 1854. (Calif. Stats. 1854, 5th sess., ch. 42/pp. 45–48)
16 Apr 1855 AMADOR gained from EL DORADO. (Calif. Stats. 1855, 6th sess., ch. 92/p. 113)
23 Apr 1855 AMADOR boundaries redefined [no change]. (Calif. Stats. 1855, 6th sess., ch. 113/p. 134–135)
25 Apr 1857 AMADOR exchanged with EL DORADO. (Calif. Stats. 1857, 8th sess., ch. 220/p. 251)
08 Apr 1863 AMADOR gained from EL DORADO. (Calif. Stats. 1863, 14th sess., ch. 170/p. 231)
16 Mar 1864 AMADOR lost to creation of ALPINE. (Calif. Stats. 1863–1864, 15th sess., ch. 180/pp. 178–182)
02 Mar 1866 AMADOR lost to MONO the remnant of territory that was left separate from AMADOR by the creation of ALPINE. (Calif. Stats. 1865, 16th sess., ch. 161/p. 144)
30 Jun 1991 AMADOR gained small area from EL DORADO. Ordinance passed 25 June 1991; effective 30 June 1991[for location see 1991_pt.shp; change too small to display on interactive map]. (Minutes of the Board of Supervisors, El Dorado County, 25 June 1991, resolution 211–91; Minutes of the Board of Supervisors, Amador County, 12 June 1990, resolution 90–182)
17 Nov 1995 AMADOR lost small area to ALPINE. Ordinance passed 3 October 1995; effective 17 November 1995 [for location see 1995_pt.shp; change too small to display on interactive map]. (Minutes of the Board of Supervisors, Amador County, 3 October 1995, ordinance 1390)
BRANCIFORTE (see SANTA CRUZ)
30 Apr 1855 Legislature authorized creation of BUENA VISTA (proposed) from TULARE; creation did not take effect. (Calif. Stats. 1855, 6th sess., ch. 161/pp. 203–205; Coy, 15–16)
16 Apr 1856 Legislature authorized BUENA VISTA (proposed) to gain from TULARE, even though the creation of BUENA VISTA (authorized 30 April 1855) had never gone into effect. [Proposed change not displayed on interactive map; see "Special Topics."] (Calif. Stats. 1856, 7th sess., ch. 81/p. 96)
18 Feb 1850 BUTTE created from non-county area. COLUSI (now COLUSA) not fully organized, attached to BUTTE "for judicial purposes." (Calif. Stats. 1849, 1st sess., ch. 15, sec. 21/p. 62)
10 Jan 1851 COLUSI (now COLUSA) fully organized, detached from BUTTE. (Rogers, 57–61)
25 Apr 1851 BUTTE gained from SUTTER, lost small area to SHASTA. (Calif. Stats. 1851, 2d sess., ch. 14, sec. 21/p. 177)
03 May 1852 BUTTE exchanged with SUTTER. (Calif. Stats. 1852, 3d sess., ch. 149/p. 237)
19 Mar 1853 BUTTE boundaries clarified [no change]. (Calif. Stats. 1853, 4th sess., ch. 37/p. 53)
31 Mar 1854 BUTTE lost to SUTTER. (Calif. Stats. 1854, 5th sess., ch. 16/p. 26)
01 Apr 1854 BUTTE lost to creation of PLUMAS. (Calif. Stats. 1854, 5th sess., ch. 1/pp. 129–131)
09 Apr 1856 BUTTE lost to creation of TEHAMA. (Calif. Stats. 1856, 7th sess., ch. 100/pp. 118–119)
19 Apr 1856 BUTTE lost to COLUSI (now COLUSA). (Calif. Stats. 1856, 7th sess., ch. 105/p. 124)
21 Apr 1856 BUTTE lost to SUTTER. (Calif. Stats. 1856, 7th sess., ch. 150/p. 231)
19 Apr 1859 BUTTE gained from TEHAMA. (Calif. Stats. 1859, 10th sess., ch. 322/p. 359)
22 Mar 1860 BUTTE lost small area in village of Strawberry Valley to YUBA [for location see 1860_pt.shp; change too small to display on interactive map]. (Calif. Stats. 1860, 11th sess., ch. 145/p. 115)
15 Apr 1861 BUTTE lost small area at Woodville to YUBA [for location see 1861_pt.shp; change too small to display on interactive map]. (Calif. Stats. 1861, 12th sess., ch. 166/p. 167)
01 Apr 1864 BUTTE lost to SUTTER. (Calif. Stats. 1863–1864, 15th sess., ch. 292/p. 301)
01 Jan 1873 BUTTE gained from COLUSA. (Political Code 1872, 1: secs. 3916, 3922/pp. 119, 123–124)
07 Mar 1874 BUTTE boundaries clarified [no change]. (Calif. Stats. 1873, 20th sess., Acts Amendatory of the Codes, p. 167)
25 Feb 1897 BUTTE exchanged with YUBA. (Calif. Stats. 1897, 32d sess., ch. 26/p. 22)
23 Mar 1901 BUTTE exchanged with PLUMAS. (Calif. Stats. 1901, 34th sess., ch. 146/pp. 549–551)
08 Aug 1915 BUTTE gained small area in section 3, township 19 north, range 1 east from GLENN [for location see 1915_pt.shp; change too small to display on interactive map]. (Calif. Stats. 1915, 41st sess., ch. 532/p. 898)
20 Nov 1944 BUTTE exchanged with TEHAMA. (Coy, 339, 345)
18 Feb 1850 CALAVERAS created from non-county area. (Calif. Stats. 1849, 1st sess., ch. 15, sec. 25/p. 63)
18 Apr 1850 CALAVERAS boundaries clarified [no change]. (Calif. Stats. 1849, 1st sess., ch. 111/pp. 262–263)
25 Apr 1851 CALAVERAS boundaries redefined [no change]. (Calif. Stats. 1851, 2d sess., ch. 14, sec. 13/p. 175)
14 Jun 1854 CALAVERAS lost to creation of AMADOR. Act passed 11 May 1854; referendum for or against creation of the new county held 14 June 1854. (Calif. Stats. 1854, 5th sess., ch. 42/pp. 45–48)
19 Apr 1856 CALAVERAS lost to creation of FREZNO (now FRESNO). (Calif. Stats. 1856, 7th sess., ch. 127/pp. 183)
24 Apr 1861 CALAVERAS lost to creation of MONO. (Calif. Stats. 1861, 12th sess., ch. 233/pp. 235–236)
16 Mar 1864 CALAVERAS lost to creation of ALPINE. (Calif. Stats. 1863–1864, 15th sess., ch. 180/pp. 178–182)
18 Feb 1850 COLUSI (now COLUSA) created from non-county area; COLUSI not fully organized, attached to BUTTE "for judicial purposes." (Calif. Stats. 1849, 1st sess., ch. 15, sec. 22/p. 62)
10 Jan 1851 COLUSI (now COLUSA) fully organized, detached from BUTTE. (Rogers, 57–61)
25 Apr 1851 COLUSI (now COLUSA) gained from YOLO, lost to SHASTA. (Calif. Stats. 1851, 2d sess., ch. 14, sec. 29/p. 179)
09 Apr 1856 COLUSI (now COLUSA) lost to creation of TEHAMA. (Calif. Stats. 1856, 7th sess., ch. 100/pp. 118–119)
19 Apr 1856 COLUSI (now COLUSA) gained from BUTTE, SUTTER, and YOLO. (Calif. Stats. 1856, 7th sess., ch. 105/p. 124)
19 Feb 1857 COLUSI (now COLUSA) gained from TEHAMA. (Calif. Stats. 1857, 8th sess., ch. 37/p. 25)
by Jan 1859 By January 1859, the spelling of "COLUSI" changed to "COLUSA." (Calif. Stats. 1859, 10th sess.; [Green], 44–45)
19 Apr 1859 COLUSA lost to TEHAMA. (Calif. Stats. 1859, 10th sess., ch. 322/p. 359)
24 Mar 1868 COLUSA lost to LAKE. (Calif. Stats. 1867, 17th sess., ch. 257/p. 269)
01 Jan 1873 COLUSA gained from TEHAMA, lost to BUTTE. (Political Code 1872, 1: secs. 3915–3916, 3922/pp. 118–119, 123–124)
31 Mar 1891 COLUSA lost small area to SUTTER [for location see 1891_pt.shp; change too small to display on interactive map]. (Calif. Stats. 1891, 29th sess., ch. 240/p. 455)
05 May 1891 COLUSA lost to creation of GLENN. Act passed 11 March 1891; referendum for or against creation of the new county held 5 May 1891. (Calif. Stats. 1891, 29th sess., ch. 94/pp. 98–101)
11 Mar 1893 COLUSA gained from GLENN. (Calif. Stats. 1893, 30th sess., ch. 141/p. 158)
13 Mar 1909 Boundary of LAKE with COLUSA and MENDOCINO redefined [no change]. (Calif. Stats. 1909, 38th sess., ch. 211/pp. 326–328)
COLUSI (see COLUSA)
18 Feb 1850 CONTRA COSTA created from non-county area. (Calif. Stats. 1849, 1st sess., ch. 15, sec. 10/p. 60)
05 Apr 1850 CONTRA COSTA boundaries clarified [no change]. (Calif. Stats. 1849, 1st sess., ch. 61, sec. 4/p. 156)
25 Apr 1851 CONTRA COSTA boundaries redefined [no change]. (Calif. Stats. 1851, 2d sess., ch. 14, sec. 10/p. 174)
14 Feb 1852 CONTRA COSTA lost to SAN JOAQUIN. (Calif. Stats. 1852, 3d sess., chs. 105–106/pp. 178–180; Purcell, 250)
25 Mar 1853 CONTRA COSTA lost to creation of ALAMEDA, and lost small remnant to SANTA CLARA. (Calif. Stats. 1853, 4th sess., ch. 41/pp. 56–59)
26 Mar 1868 CONTRA COSTA gained the Brothers Islands from MARIN. (Calif. Stats. 1867, 17th sess., ch. 305/p. 347)
14 Jan 1958 CONTRA COSTA lost small area to ALAMEDA [for location see 1958_pt.shp; change too small to display on interactive map]. (Coy, 338–339)
01 Sep 1992 CONTRA COSTA lost small area to ALAMEDA. Ordinance passed 11 August 1992; effective 1 September 1992 [for location see 1992_pt.shp; change too small to display on interactive map]. (Minutes of the Board of Supervisors, Alameda County, 11 August 1992, ordinance 92–57)
04 Oct 1995 CONTRA COSTA gained small area from ALAMEDA [for location see 1995_pt.shp; change too small to display on interactive map]. (Calif. Stats. 1995, reg. sess., ch. 529, sec. 3 in Official California Legislative Information, http://www.leginfo.ca.gov/statute.html, 23 September 2002)
04 Apr 1864 Legislature authorized creation of COSO from MONO and TULARE; creation did not take effect [see creation of INYO, 22 March 1866]. (Calif. Stats. 1863–1864, 15th sess., ch. 470/pp. 528–530)
02 Mar 1857 DEL NORTE created from KLAMATH (extinct) and a small area of SISKIYOU. (Calif. Stats. 1857, 8th sess., ch. 52/pp. 35–36)
11 Feb 1858 DEL NORTE boundaries clarified [no change]. (Calif. Stats. 1858, 9th sess., ch. 23/p. 21)
01 Jan 1873 DEL NORTE exchanged with SISKIYOU. (Political Code 1872, 1: secs. 3909–3910, 3913/pp. 113–115, 117)
11 Mar 1887 DEL NORTE exchanged with SISKIYOU. (Calif. Stats. 1887, 27th sess., ch. 88/pp. 105–107)
23 Mar 1901 DEL NORTE exchanged with HUMBOLDT. (Calif. Stats. 1901, 34th sess., ch. 193/p. 600)
18 Feb 1850 Area between BRANCIFORTE (now SANTA CRUZ) and SAN FRANCISCO was in dispute. Both counties claimed the area. (Calif. Stats. 1849, 1st sess., ch. 15, secs. 7–8/pp. 59–60; Stanger, 88)
01 Jul 1856 SAN MATEO created from SAN FRANCISCO; SAN MATEO boundary with SANTA CRUZ was in dispute [see 18 February 1850]. Dispute ended 18 April 1857 when SAN MATEO gained control over the area. (Calif. Stats. 1856, 7th sess., ch. 125/pp. 145–146, 176–178)
18 Feb 1850 EL DORADO created from non-county area. (Calif. Stats. 1849, 1st sess., ch. 15, sec. 18/pp. 61–62)
25 Apr 1851 EL DORADO boundaries redefined [no change]. (Calif. Stats. 1851, 2d sess., ch. 14, sec. 16/p. 176)
16 Apr 1855 EL DORADO lost to AMADOR. (Calif. Stats. 1855, 6th sess., ch. 92/p. 113)
25 Apr 1857 EL DORADO exchanged with AMADOR. (Calif. Stats. 1857, 8th sess., ch. 220/p. 251)
08 Apr 1863 EL DORADO lost to AMADOR. (Calif. Stats. 1863, 14th sess., ch. 170/p. 231)
20 Apr 1863 EL DORADO gained from PLACER. (Calif. Stats. 1863, 14th sess., ch. 263/p. 349)
16 Mar 1864 EL DORADO lost to creation of ALPINE. (Calif. Stats. 1863–1864, 15th sess., ch. 180/pp. 178–182)
10 Aug 1913 EL DORADO exchanged with PLACER. (Calif. Stats. 1913, 40th sess., chs. 315–316/pp. 603–605)
30 Jun 1991 EL DORADO lost small area to AMADOR. Ordinance passed 25 June 1991; effective 30 June 1991 [for location see 1991_pt.shp; change too small to display on interactive map]. (Minutes of the Board of Supervisors, El Dorado County, 25 June 1991, resolution 211–91; Minutes of the Board of Supervisors, Amador County, 12 June 1990, resolution 90–182)
19 Apr 1856 FREZNO (now FRESNO) created from CALAVERAS, MARIPOSA, MERCED, TULARE, and TUOLUMNE. (Calif. Stats. 1856, 7th sess., ch. 127/pp. 183)
11 Apr 1859 FREZNO (now FRESNO) lost to TUOLUMNE. (Calif. Stats. 1859, 10th sess., ch. 204/p. 213)
24 Apr 1861 FREZNO (now FRESNO) lost to creation of MONO. (Calif. Stats. 1861, 12th sess., ch. 233/pp. 235–236)
by Apr 1862 By April 1862, the phonetic spelling of "FREZNO" changed to "FRESNO." (Calif. Stats. 1863, 13th sess.; Gudde, 138)
29 Mar 1870 FRESNO lost to MARIPOSA. (Calif. Stats. 1869, 18th sess., ch. 341/p. 449)
01 Apr 1872 FRESNO gained from MARIPOSA. (Calif. Stats. 1871, 19th sess., ch. 602/p. 891)
11 Feb 1874 Boundary between FRESNO and MARIPOSA redefined [no change]. (Calif. Stats. 1873, 20th sess., ch. 88/p. 100)
27 Mar 1874 FRESNO exchanged with TULARE. (Calif. Stats. 1873, 20th sess., ch. 468/p. 700)
23 Mar 1876 FRESNO exchanged with TULARE. (Calif. Stats. 1875, 21st sess., ch. 301/p. 397)
11 Mar 1887 FRESNO lost to SAN BENITO. (Calif. Stats. 1887, 27th sess., ch. 86/p.103)
16 May 1893 FRESNO lost to creation of MADERA. Act passed 11 March 1893; referendum for or against creation of new county held 16 May 1893. (Calif. Stats. 1893, 30th sess., ch. 143/pp. 168–172; California USGenWeb Project, Madera County, http://www.cagenweb.com/madera/MadHistory.html, 17 July 2002; "Mariposa County v. Madera County," in Calif. Rpts., 142:50–58)
14 Mar 1907 Legislature authorized KINGS to gain from FRESNO, dependent on local referendum. Referendum failed [no change]. [Proposed change not displayed on interactive map; see "Special Topics."] (Calif. Stats. 1907, 37th sess., ch. 214/pp. 260–263; Coy, 51–52; "Wheeler v. Herbert," in Calif. Rpts., 152:224–241)
12 Apr 1909 FRESNO lost to KINGS. (Calif. Stats. 1909, 38th sess., ch. 483/pp. 827–829)
31 Dec 1986 FRESNO gained small area from TULARE. Ordinance passed 18 November 1986; effective 31 December 1986 [for location see 1986_pt.shp; change too small to display on interactive map]. (Minutes of the Board of Supervisors, Tulare County, 18 November 1986, ordinance 2745)
30 Sep 1991 FRESNO exchanged small areas with TULARE. Ordinance passed 3 September 1991; effective 30 September 1991 [for location see 1991_pt.shp; change too small to display on interactive map]. (Minutes of the Board of Supervisors, Tulare County, 3 September 1991, ordinance 2970)
FREZNO (see FRESNO)
05 May 1891 GLENN created from COLUSA. Act passed 11 March 1891; referendum for or against creation of the new county held 5 May 1891. (Calif. Stats. 1891, 29th sess., ch. 94/pp. 98–101)
11 Mar 1893 GLENN lost to COLUSA. (Calif. Stats. 1893, 30th sess., ch. 141/p. 158)
08 Mar 1907 GLENN gained from MENDOCINO. (Calif. Stats. 1907, 37th sess., ch. 113/p. 135)
13 Mar 1909 GLENN exchanged with LAKE. (Calif. Stats. 1909, 38th sess., ch. 211, sec. 2/p. 327)
08 Aug 1915 GLENN lost small area in section 3, township 19 north, range 1 east to BUTTE [for location see 1915_pt.shp; change too small to display on interactive map]. (Calif. Stats. 1915, 41st sess., ch. 532/p. 898)
12 May 1853 HUMBOLDT created from TRINITY. (Calif. Stats. 1853, 4th sess., ch. 114/pp. 161–164)
11 Mar 1859 HUMBOLDT lost to MENDOCINO. (Calif. Stats. 1859, 10th sess., ch. 108/pp. 98–99)
28 Apr 1860 HUMBOLDT gained from MENDOCINO. (Calif. Stats. 1860, 11th sess., ch. 340/p. 334)
11 Feb 1862 HUMBOLDT boundaries redefined [no change]. (Calif Laws 1862, 13th sess., ch. 11/p. 6)
30 May 1874 HUMBOLDT gained part of KLAMATH; KLAMATH eliminated. Act passed 28 March 1874; referendum for annexation of KLAMATH held 30 May 1874. (Calif. Stats. 1873, 20th sess., ch. 520/pp. 755–758; Kasch, 270–272)
23 Mar 1901 HUMBOLDT exchanged with DEL NORTE, lost small area to SISKIYOU. (Calif. Stats. 1901, 34th sess., ch. 193/p. 600)
12 Aug 1907 IMPERIAL created from SAN DIEGO. (Coy, 50–51; Farr, 18–19)
16 Jun 1967 IMPERIAL boundaries redefined to more precisely define the boundary between IMPERIAL and the State of Arizona [no discernible change]. (Calif. Stats. 1967, reg. sess., ch. 339/pp. 1536–1537; Coy, 339)
22 Mar 1866 INYO created from MONO and TULARE. INYO boundaries were identical to those of COSO (proposed) [see 4 April 1864]. (Calif. Stats. 1865, 16th sess., ch. 316/pp. 355–358)
28 Mar 1870 INYO gained from MONO. (Calif. Stats. 1869, 18th sess., ch. 323/p. 421)
01 Jan 1873 INYO gained from KERN and SAN BERNARDINO. (Political Code 1872, 1: secs. 3941–3943/pp. 139–140)
19 Sep 1947 Boundary between INYO and SAN BERNARDINO placed in dispute. Section 23136 of Political Code was revised to authorize SAN BERNARDINO to gain from INYO a strip of territory one and one-half miles wide between the San Bernardino Meridian and the state line. The companion description of INYO boundaries in section 23114 authorized no such change [no change]. (Calif. Stats. 1947, reg. sess., ch. 424, secs. 23114, 23136/pp. 1050, 1068)
11 Sep 1957 INYO lost small area to SAN BERNARDINO; boundaries of INYO and SAN BERNARDINO clarified, ending boundary dispute dating from 1947. (Calif. Stats. 1957, reg. sess., ch. 2382/p. 4119)
1972 In 1972, boundary between INYO and SAN BERNARDINO was adjusted [precise location unknown, not mapped]. (Correspondence, California State Board of Equalization, 25 July 2002)
02 Apr 1866 KERN created from LOS ANGELES and TULARE. (Calif. Stats. 1865, 16th sess., ch. 569/pp. 796–798)
10 Feb 1868 KERN gained from TULARE. (Calif. Stats. 1867, 17th sess., ch. 43/p. 40)
01 Jan 1873 KERN lost to INYO and TULARE. Boundary with VENTURA adjusted to run partially on public land survey lines. (Political Code 1872, 1: secs. 3940–3942/pp. 138–139)
14 Mar 1885 KERN exchanged with SAN LUIS OBISPO. (Calif. Stats. 1885, 26th sess., ch. 149/pp. 139–141)
27 Jul 1917 KERN lost to SAN BERNARDINO. (Calif. Stats. 1917, 42d sess., ch. 205/p. 301)
23 Jul 1919 KERN gained from VENTURA when boundary was adjusted to run on public land survey lines. The California Supreme Court declared this chapter unconstitutional on 19 February 1920, but this particular change appears to have remained in effect; change confirmed in 1923 by reenactment of the 1919 law. (Calif. Stats. 1919, 43d sess., ch. 470, secs. 3923, 3964/pp. 870, 908–909; "Mundell v. Lyons," in Calif. Rpts., 182:289–293; Calif. Laws 1923, 45th sess., ch. 160, secs. 16, 57/pp. 336, 373)
16 May 1923 KERN boundaries redefined; see 23 July 1919 [no change]. (Calif. Laws 1923, 45th sess., ch. 160, secs. 16, 57/pp. 336, 373)
13 May 1963 KERN exchanged small areas with SAN BERNARDINO. (Coy, 340, 342; correspondence, California Board of Equalization, 25 July 2002)
31 Dec 1986 KERN gained small area from VENTURA [precise location unknown, not mapped]. (Minutes of the Board of Supervisors, Kern County, 4 November 1986, ordinance G–4345)
10 Jun 1991 KERN gained from VENTURA. (Calif. Stats. 1991–1992, reg. sess., ch. 51/p. 150)
23 May 1893 KINGS created from TULARE. Act passed 22 March 1893; referendum for or against creation of new county held 23 May 1893. (Calif. Stats. 1893, 30th sess., ch. 150/pp. 176–181; Kings County History, http://calflytech.com/kingshistory.html, 18 July 2002)
14 Mar 1907 Legislature authorized KINGS to gain from FRESNO, dependent on local referendum. Referendum failed [no change]. [Proposed change not displayed on interactive map; see "Special Topics."] (Calif. Stats. 1907, 37th sess., ch. 214/pp. 260–263; Coy, 51–52; "Wheeler v. Herbert," in Calif. Rpts., 152:224–241)
12 Apr 1909 KINGS gained from FRESNO. (Calif. Stats. 1909, 38th sess., ch. 483/pp. 827–829)
25 Apr 1851 KLAMATH (extinct) created from TRINITY. (Calif. Stats. 1851, 2d sess., ch. 14, sec. 31/p. 180)
22 Mar 1852 KLAMATH (extinct) lost to creation of SISKIYOU. (Calif. Stats. 1852, 3d sess., ch. 146/pp. 233–235)
30 Apr 1855 KLAMATH (extinct) lost to TRINITY. (Calif. Stats. 1855, 6th sess., ch. 156/p. 200)
02 Mar 1857 KLAMATH (extinct) lost to creation of DEL NORTE. (Calif. Stats. 1857, 8th sess., ch. 52/pp. 35–36)
30 May 1874 KLAMATH lost all territory to HUMBOLDT and SISKIYOU; KLAMATH eliminated. Act passed 28 March 1874; referendum for annexation of KLAMATH held 30 May 1874. (Calif. Stats. 1873, 20th sess., ch. 520/pp. 755–758; Kasch, 270–272)
20 May 1861 LAKE created from NAPA. (Calif. Stats. 1861, 12th sess., ch. 498/pp. 560–561)
29 Feb 1864 LAKE gained from MENDOCINO and NAPA. (Calif. Stats. 1863–1864, 15th sess., ch. 122/p. 111)
24 Mar 1868 LAKE gained from COLUSA, NAPA, and YOLO. (Calif. Stats. 1867, 17th sess., ch. 257/p. 269)
08 Mar 1872 LAKE lost to NAPA. (Calif. Stats. 1871, 19th sess., ch. 229/p. 305)
08 Mar 1907 LAKE lost to MENDOCINO. (Calif. Stats. 1907, 37th sess., ch. 113/p. 135)
13 Mar 1909 LAKE exchanged with GLENN; boundary of LAKE with COLUSA and MENDOCINO redefined [no change]. (Calif. Stats. 1909, 38th sess., ch. 211/pp. 326–328)
31 Jul 1917 LAKE exchanged with MENDOCINO. (Calif. Stats. 1917, 42d sess., ch. 779/pp. 1635–1640)
01 Apr 1864 LASSEN created from PLUMAS and SHASTA. (Calif. Stats. 1863–1864, 15th sess., ch. 261/pp. 264–269)
26 Mar 1866 LASSEN boundaries clarified [no change]. (Calif. Stats. 1865, 16th sess., ch. 371/p. 453)
01 Jan 1873 LASSEN gained from PLUMAS. (Political Code 1872, 1: secs. 3912, 3920/pp. 115–116, 122–123)
16 Mar 1874 LASSEN lost small area to SIERRA when boundary was set on public land survey lines. (Calif. Stats. 1873, 20th sess., Acts Amendatory of the Codes, p. 166)
14 Mar 1899 LASSEN gained from SHASTA. (Calif. Stats. 1899, 33d sess., ch. 82/p. 98)
28 Feb 1901 LASSEN exchanged with PLUMAS. (Calif. Stats. 1901, 34th sess., ch. 61/pp. 76–80)
18 Feb 1850 LOS ANGELES created from non-county area. (Calif. Stats. 1849, 1st sess., ch. 15, sec. 3/p. 59)
25 Apr 1851 LOS ANGELES gained from MARIPOSA, exchanged with SAN DIEGO and SANTA BARBARA. (Calif. Stats. 1851, 2d sess., ch. 14, sec. 3/p. 172)
26 Apr 1853 LOS ANGELES lost to creation of SAN BERNARDINO. (Calif. Stats. 1853, 4th sess., ch. 78/pp. 119–123)
26 Mar 1856 LOS ANGELES boundaries redefined [no change]. (Calif. Stats. 1856, 7th sess., ch. 46/p. 53)
02 Apr 1866 LOS ANGELES lost to creation of KERN. (Calif. Stats. 1865, 16th sess., ch. 569/pp. 796–798)
01 Jan 1873 LOS ANGELES lost to SAN DIEGO. (Political Code 1872, 1: secs. 3944–3945/pp. 140–142)
05 Feb 1877 LOS ANGELES lost to SAN BERNARDINO as a result of an official survey of the boundary. (Coy, 149, 217–219)
Jul 1881 In July 1881, LOS ANGELES lost to VENTURA as a result of an official boundary survey. (Coy, 150–154, 292)
04 Jun 1889 LOS ANGELES lost to creation of ORANGE. Act passed 11 March 1889; referendum for or against creation of new county held 4 June 1889. (Calif. Stats. 1889, 28th sess., ch. 110/pp. 123–129)
23 Jul 1919 The new Political Code authorized LOS ANGELES to exchange with VENTURA. This chapter of the 1919 revision of the laws did not take effect and was found unconstitutional by the California Supreme Court, 19 February 1920. [Proposed change not displayed on interactive map; see "Special Topics."] (Calif. Stats. 1919, 43d sess., ch. 470, secs. 3927, 3964/pp. 877–879, 908–909; "Mundell v. Lyons," in Calif. Rpts., 182:289–293; Coy, 152-153)
01 Sep 1987 LOS ANGELES lost small area in Cypress Memorial Park Cemetery to ORANGE. Ordinance passed 29 July 1987; effective 1 September 1987 [for location see 1987_pt.shp; change too small to display on interactive map]. (Minutes of the Board of Supervisors, Orange County, 29 July 1987, ordinance 3647)
01 Mar 1992 LOS ANGELES lost small area to SAN BERNARDINO. Ordinance passed 27 January 1992; effective 1 March 1992 [for location see 1992_pt.shp; change too small to display on interactive map]. (Minutes of the Board of Supervisors, San Bernardino County, 27 January 1992, ordinance 3478)
11 Oct 1993 LOS ANGELES lost small area to SAN BERNARDINO [for location see 1993_pt.shp; change too small to display on interactive map]. (Calif. Stats. 1993–1994, reg. sess., ch. 1195, sec. 3/p. 6854)
30 Sep 1999 LOS ANGELES lost small area to ORANGE [for location see 1999_pt.shp; change too small to display on interactive map]. (Minutes of the Board of Supervisors, Los Angeles County, 24 August 1999, ordinance 99–0077M)
19 Sep 2000 Boundary between LOS ANGELES and ORANGE redefined to incorporate 1999 boundary change [no change]. (Calif. Stats. 2000, reg. sess., ch. 506, secs. 15–16 in Official California Legislative Information, http://www.leginfo.ca.gov/statute.html, 23 September 2002)
16 May 1893 MADERA created from FRESNO. Act passed 11 March 1893; referendum for or against creation of new county held 16 May 1893. (Calif. Stats. 1893, 30th sess., ch. 143/pp. 168–172; California USGenWeb Project, Madera County, http://www.cagenweb.com/madera/MadHistory.html, 17 July 2002; "Mariposa County v. Madera County," in Calif. Rpts., 142:50–58)
03 May 1852 Mare Island was inadvertently left outside the jurisdiction of any county when SONOMA boundaries were redefined. It remained a non-county area until it became part of SOLANO on 27 January 1853. (Calif. Stats. 1852, 3d sess., ch. 147/p. 236)
18 Feb 1850 MARIN created from non-county area; MARIN not fully organized, attached to SONOMA "for judicial purposes." (Calif. Stats. 1849, 1st sess., ch. 15, sec. 11/p. 60)
22 Apr 1850 MARIN fully organized, detached from SONOMA. (Calif. Stats. 1849, 1st sess., ch. 131/p. 406)
25 Apr 1851 MARIN boundaries redefined [no change]. (Calif. Stats. 1851, 2d sess., ch. 14, sec. 23/pp. 177–178)
15 May 1854 MARIN gained "Island of Los Angeles" (Angel Island) in San Francisco Bay from SAN FRANCISCO. (Calif. Stats. 1854, 5th sess., ch. 67/p. 121)
27 Apr 1855 MARIN lost to SONOMA. (Calif. Stats. 1855, 6th sess., ch. 125/p. 150)
18 Apr 1857 MARIN lost Angel Island in San Francisco Bay to SAN FRANCISCO. (Calif. Stats. 1857, 8th sess., ch. 190/pp. 209–210)
25 Apr 1860 MARIN gained from SONOMA when boundary was changed to run on road [see 13 May 1861]; MARIN gained Angel Island in San Francisco Bay from SAN FRANCISCO. (Calif. Stats. 1860, 11th sess., ch. 288/p. 269)
13 May 1861 MARIN lost to SONOMA [repealed part of act of 25 April 1860]. (Calif. Stats. 1861, 12th sess., ch. 346/p. 351)
26 Mar 1868 MARIN lost the Brothers Islands to CONTRA COSTA. (Calif. Stats. 1867, 17th sess., ch. 305/p. 347)
18 Feb 1850 MARIPOSA created from non-county area. (Calif. Stats. 1849, 1st sess., ch. 15, sec. 28/p. 63)
25 Apr 1851 MARIPOSA gained from SAN DIEGO, lost to LOS ANGELES. (Calif. Stats. 1851, 2d sess., ch. 14, sec. 15/pp. 175–176)
20 Apr 1852 MARIPOSA lost to creation of TULARE. (Calif. Stats. 1852, 3d sess., ch. 153/pp. 240–242)
19 Apr 1855 MARIPOSA lost to creation of MERCED. (Calif. Stats. 1855, 6th sess., ch. 104/pp. 125–128)
19 Apr 1856 MARIPOSA lost to creation of FREZNO (now FRESNO). (Calif. Stats. 1856, 7th sess., ch. 127/pp. 183)
24 Apr 1861 MARIPOSA lost a remnant of territory to creation of MONO. (Calif. Stats. 1861, 12th sess., ch. 233/pp. 235–236)
29 Mar 1870 MARIPOSA gained from FRESNO. (Calif. Stats. 1869, 18th sess., ch. 341/p. 449)
01 Apr 1872 MARIPOSA lost to FRESNO. (Calif. Stats. 1871, 19th sess., ch. 602/p. 891)
11 Feb 1874 Boundary between MARIPOSA and FRESNO redefined [no change]. (Calif. Stats. 1873, 20th sess., ch. 88/p. 100)
18 Feb 1850 MENDOCINO created from non-county area; MENDOCINO not fully organized, attached to SONOMA "for judicial purposes." (Calif. Stats. 1849, 1st sess., ch. 15, sec. 16/p. 61)
25 Apr 1851 MENDOCINO boundaries redefined [no change]. (Calif. Stats. 1851, 2d sess., ch. 14, sec. 26/pp. 178–179)
16 Apr 1852 MENDOCINO lost to NAPA. (Calif. Stats. 1852, 3d sess., ch. 116/p. 192)
04 Apr 1855 MENDOCINO lost to NAPA. (Calif. Stats. 1855, 6th sess., ch. 68/p. 77)
27 Apr 1855 MENDOCINO exchanged with SONOMA. (Calif. Stats. 1855, 6th sess., ch. 125/p. 150)
11 Mar 1859 MENDOCINO gained from HUMBOLDT and TRINITY, exchanged with SONOMA. (Calif. Stats. 1859, 10th sess., ch. 108/pp. 98–99)
02 May 1859 MENDOCINO fully organized, detached from SONOMA. (Calif. Stats. 1859, 10th sess., ch. 108, sec. 2/p. 99; History of Mendocino County, 272–273, 283)
28 Apr 1860 MENDOCINO lost to HUMBOLDT and TRINITY. (Calif. Stats. 1860, 11th sess., ch. 340/p. 334)
29 Feb 1864 MENDOCINO lost to LAKE. (Calif. Stats. 1863–1864, 15th sess., ch. 122/p. 111)
30 Oct 1872 MENDOCINO lost to TRINITY when their common boundary was surveyed; later MENDOCINO claimed a different boundary based on an 1891 survey. California Supreme Court upheld 1872 survey on 15 May 1907. (Calif. Stats. 1871, 19th sess., ch. 531/p. 766; "Trinity County v. Mendocino County," in Calif. Rpts., 151: 279–289)
08 Mar 1907 MENDOCINO gained from LAKE, lost to GLENN. (Calif. Stats. 1907, 37th sess., ch. 113/p. 135)
13 Mar 1909 Boundary of LAKE with MENDOCINO and COLUSA redefined [no change]. (Calif. Stats. 1909, 38th sess., ch. 211/pp. 326–328)
30 Jul 1917 MENDOCINO exchanged with SONOMA. (Calif. Stats. 1917, 42d sess., ch. 725/p. 1396)
31 Jul 1917 MENDOCINO exchanged with LAKE. (Calif. Stats. 1917, 42d sess., ch. 779/pp. 1635–1640)
19 Apr 1855 MERCED created from MARIPOSA. (Calif. Stats. 1855, 6th sess., ch. 104/pp. 125–128)
19 Apr 1856 MERCED lost to creation of FREZNO (now FRESNO) and lost to TULARE. (Calif. Stats. 1856, 7th sess., ch. 127/pp. 183)
08 Mar 1866 Legislature authorized a re-survey of the MERCED-STANISLAUS line, established in 1854, which would have resulted in MERCED gaining from STANISLAUS. Gain did not take effect; see 13 February 1868. [Proposed change not displayed on interactive map; see "Special Topics."] (Calif. Stats. 1865, 16th sess., ch. 191/p. 172; Outcalt, 118–119, 122–123)
13 Feb 1868 Boundary between MERCED and STANISLAUS redefined to confirm 1854 STANISLAUS line; see 8 March 1866 [no change]. (Calif. Stats. 1867, 17th sess., ch. 57/p. 56)
11 Mar 1887 MERCED lost small area to SAN BENITO. (Calif. Stats. 1887, 27th sess., ch. 86/p.103)
17 Feb 1874 MODOC created from SISKIYOU. (Calif. Stats. 1873, 20th sess., ch. 107/pp. 124–129)
24 Apr 1861 MONO created from CALAVERAS, FREZNO (now FRESNO), and remnant of MARIPOSA. Due to uncertainty about the precise location of the boundary between California and Nevada Territory, the county seat of MONO, Aurora, was actually located in Nevada. (Calif. Stats. 1861, 12th sess., ch. 233/pp. 235–236; Chappell, 239–242; "Reddy v. Tinkum," in Calif. Rpts., 60:458–467)
16 Mar 1864 MONO lost to creation of ALPINE. (Calif. Stats. 1863–1864, 15th sess., ch. 180/pp. 178–182)
04 Apr 1864 Legislature authorized creation of COSO from MONO and TULARE; creation did not take effect [see creation of INYO, 22 March 1866]. (Calif. Stats. 1863–1864, 15th sess., ch. 470/pp. 528–530)
02 Mar 1866 MONO gained remnant of AMADOR that was left separate from the rest of AMADOR after the creation of ALPINE. (Calif. Stats. 1865, 16th sess., ch. 161/p. 144)
22 Mar 1866 MONO lost to creation of INYO; INYO boundaries were identical to those of COSO (proposed) [see 4 April 1864]. (Calif. Stats. 1865, 16th sess., ch. 316/pp. 355–358)
22 Jan 1870 MONO gained from TULARE the remnant of territory that was separated from TULARE by the creation of INYO on 22 March 1866. (Calif. Stats. 1869, 18th sess., ch. 18/p. 20)
28 Mar 1870 MONO lost to INYO. (Calif. Stats. 1869, 18th sess., ch. 323/p. 421)
18 Feb 1850 MONTEREY created from non-county area. (Calif. Stats. 1849, 1st sess., ch. 15, sec. 6/p. 59)
25 Apr 1851 MONTEREY exchanged with SAN LUIS OBISPO. (Calif. Stats. 1851, 2d sess., ch. 14, sec. 6/p. 173)
13 May 1861 MONTEREY lost to SAN LUIS OBISPO. (Calif. Stats. 1861, 12th sess., ch. 342/p. 349)
20 Apr 1863 MONTEREY gained from SAN LUIS OBISPO. (Calif. Stats. 1863, 14th sess., ch. 276/p. 358)
12 Feb 1874 MONTEREY lost to creation of SAN BENITO. (Calif. Stats. 1873, 20th sess., ch. 87/pp. 95–99)
18 Feb 1850 NAPA created from non-county area. (Calif. Stats. 1849, 1st sess., ch. 15, sec. 15/p. 61)
25 Apr 1851 NAPA boundaries redefined [no change]. (Calif. Stats. 1851, 2d sess., ch. 14, sec. 25/p. 178)
16 Apr 1852 NAPA gained from MENDOCINO. (Calif. Stats. 1852, 3d sess., ch. 116/p. 192)
04 Apr 1855 NAPA gained from MENDOCINO, SOLANO, and SONOMA. (Calif. Stats. 1855, 6th sess., ch. 68/p. 77)
20 May 1861 NAPA lost to creation of LAKE. (Calif. Stats. 1861, 12th sess., ch. 498/pp. 560–561)
29 Feb 1864 NAPA lost to LAKE. (Calif. Stats. 1863–1864, 15th sess., ch. 122/p. 111)
24 Mar 1868 NAPA lost small area to LAKE. (Calif. Stats. 1867, 17th sess., ch. 257/p. 269)
08 Mar 1872 NAPA gained from LAKE. (Calif. Stats. 1871, 19th sess., ch. 229/p. 305)
25 Apr 1851 NEVADA created from YUBA. (Calif. Stats. 1851, 2d sess., ch. 14, sec. 20/p. 177)
03 May 1852 NEVADA gained from SIERRA. (Calif. Stats. 1852, 3d sess., chs. 114–115/pp. 190–192)
19 Apr 1856 NEVADA gained from SIERRA. (Calif. Stats. 1856, 7th sess., ch. 122/p. 143)
28 Dec 1908 California Supreme Court settled boundary dispute between NEVADA and SIERRA in favor of SIERRA. Dispute grew out of disagreement over the location of the source of the South Fork of Middle Yuba River [no change]. ("Sierra County v. Nevada County," in Calif. Rpts., 155:1–15)
01 Mar 1909 NEVADA boundary with SIERRA clarified to run on public land survey lines [no discernible change]. (Calif. Stats. 1909, 38th sess., ch. 75, sec. 2/p. 86)
04 Jun 1889 ORANGE created from LOS ANGELES. Act passed 11 March 1889; referendum for or against creation of new county held 4 June 1889. (Calif. Stats. 1889, 28th sess., ch. 110/pp. 123–129)
01 Sep 1987 ORANGE gained small area in Cypress Memorial Park Cemetery from LOS ANGELES. Ordinance passed 29 July 1987; effective 1 September 1987 [for location see 1987_pt.shp; change too small to display on interactive map]. (Minutes of the Board of Supervisors, Orange County, 29 July 1987, ordinance 3647)
08 Nov 1988 ORANGE exchanged small areas with RIVERSIDE. Ordinance passed 27 September 1988; effective 8 November 1988. (Minutes of the Board of Supervisors, Riverside County, 27 September 1988, ordinance 665)
01 Jul 1992 Boundary between ORANGE and RIVERSIDE restated [no change]. Ordinance passed 26 November 1991; effective 1 July 1992. (Minutes of the Board of Supervisors, Riverside County, 26 November 1991, ordinance 717)
11 Oct 1993 ORANGE boundaries redefined [no change]. (Calif. Stats. 1993–1994, reg. sess., ch. 1195, sec. 4/pp. 6855–6858)
30 Sep 1999 ORANGE gained small area from LOS ANGELES [for location see 1999_pt.shp; change too small to display on interactive map]. (Minutes of the Board of Supervisors, Los Angeles County, 24 August 1999, ordinance 99–0077M)
19 Sep 2000 Boundary between ORANGE and LOS ANGELES redefined to incorporate 1999 boundary change [no change]. (Calif. Stats. 2000, reg. sess., ch. 506, secs. 15–16 in Official California Legislative Information, http://www.leginfo.ca.gov/statute.html, 23 September 2002)
03 May 1852 California Legislature proposed creation of PAUTAH in Utah Territory (present Nevada). Creation never took effect because the United States never ceded the area to California. (Calif. Stats. 1852, 3d sess., ch. 118/p. 193; "Historical and Political Data, Carson County, Utah Territory," Political History of Nevada 1996, http://dmla.clan.lib.nv.us/docs/nsla/archives/political/historical/hist05.htm, 12 December 2002)
08 Apr 1859 PAUTAH legally eliminated; ended the attempt by California to gain part of Utah Territory (present Nevada). (Calif. Stats. 1859, 10th sess., ch. 183/p. 186)
25 Apr 1851 PLACER created from SUTTER and YUBA. (Calif. Stats. 1851, 2d sess., ch. 14, sec. 17/p. 176)
20 Apr 1863 PLACER lost to EL DORADO. (Calif. Stats. 1863, 14th sess., ch. 263/p. 349)
13 Mar 1866 PLACER exchanged with SUTTER. (Calif. Stats. 1865, 16th sess., ch. 224/p. 223)
01 Jan 1873 PLACER gained small area from SUTTER. (Political Code 1872, 1: sec. 3924, 3926/pp. 125–127)
19 Mar 1889 PLACER boundaries clarified [no change]. (Calif. Stats. 1889, 28th sess., ch. 262/p. 402)
10 Aug 1913 PLACER exchanged with EL DORADO. (Calif. Stats. 1913, 40th sess., chs. 315–316/pp. 603–605)
01 Apr 1854 PLUMAS created from BUTTE. (Calif. Stats. 1854, 5th sess., ch. 1/pp. 129–131)
27 Mar 1863 PLUMAS lost to SIERRA. (Calif. Stats. 1863, 14th sess., ch. 101/p. 114; Sinnott, 6:19–22)
01 Apr 1864 PLUMAS lost to creation of LASSEN. (Calif. Stats. 1863–1864, 15th sess., ch. 261/pp. 264–269)
31 Mar 1866 PLUMAS gained from SIERRA and gained small area from YUBA. (Calif. Stats. 1865, 16th sess., ch. 466/p. 605)
28 Mar 1868 PLUMAS lost small area to SIERRA. (Calif. Stats. 1867, 17th sess., ch. 377/p. 462)
01 Jan 1873 PLUMAS lost to LASSEN and SHASTA. (Political Code 1872, 1: secs. 3911–3912, 3920/pp. 115–116, 122–123)
16 Mar 1874 PLUMAS lost small area to SIERRA when boundary was set on public land survey lines. (Calif. Stats. 1873, 20th sess., Acts Amendatory of the Codes, p. 166)
28 Feb 1901 PLUMAS exchanged with LASSEN. (Calif. Stats. 1901, 34th sess., ch. 61/pp. 76–80)
23 Mar 1901 PLUMAS exchanged with BUTTE; boundary between PLUMAS and SHASTA clarified to run on public land survey line [no discernible change]. (Calif. Stats. 1901, 34th sess., chs. 146, 171/pp. 549–551, 560)
02 May 1893 RIVERSIDE created from SAN BERNARDINO and SAN DIEGO. Act passed 11 March 1893; referendum for or against creation of new county held 2 May 1893. (Calif. Stats. 1893, 30th sess., ch. 142/pp. 158–168)
22 Jul 1919 RIVERSIDE exchanged with SAN BERNARDINO. (Calif. Stats. 1919, 43d sess., ch. 62/p. 99)
16 Jun 1967 RIVERSIDE boundaries redefined to more precisely define the boundary between RIVERSIDE and the State of Arizona [no discernible change]. (Calif. Stats. 1967, reg. sess., ch. 340/pp. 1537–1539; Coy, 340)
08 Nov 1988 RIVERSIDE exchanged small areas with ORANGE. Ordinance passed 27 September 1988; effective 8 November 1988. (Minutes of the Board of Supervisors, Riverside County, 27 September 1988, ordinance 665)
01 Jul 1992 Boundary between RIVERSIDE and ORANGE restated [no change]. Ordinance passed 26 November 1991; effective 1 July 1992. (Minutes of the Board of Supervisors, Riverside County, 26 November 1991, ordinance 717)
11 Oct 1993 RIVERSIDE boundaries redefined [no change]. (Calif. Stats. 1993–1994, reg. sess., ch. 1195, sec. 5/pp. 6858–6860)
18 Feb 1850 SACRAMENTO created from non-county area. (Calif. Stats. 1849, 1st sess., ch. 15, sec. 17/p. 61; Tinkham, 64)
25 Apr 1851 SACRAMENTO boundaries redefined [no change]. (Calif. Stats. 1851, 2d sess., ch. 14, sec. 11/p. 174)
30 Mar 1857 SACRAMENTO boundaries redefined [no change]. (Calif. Stats. 1857, 8th sess., ch. 120/p. 132)
23 Apr 1861 SACRAMENTO gained from SAN JOAQUIN. (Calif. Stats. 1861, 12th sess., ch. 219/p. 221; Tinkham, 64–65)
13 Mar 1866 SACRAMENTO boundaries redefined [no change]. (Calif. Stats. 1865, 16th sess., ch. 224/p. 223)
12 Mar 1870 SACRAMENTO gained small areas from SOLANO and YOLO. (Calif. Stats. 1869, 18th sess., ch. 191/p. 294)
01 Apr 1878 SACRAMENTO lost to SAN JOAQUIN. (Calif. Stats. 1877, 22d sess., Acts Amendatory of the Political Code, ch. 636/p. 70)
18 Mar 1905 Boundary between SACRAMENTO and SAN JOAQUIN redefined [no change]. (Calif. Stats. 1905, 36th sess., ch. 167/p. 164)
14 Jul 1988 SACRAMENTO boundaries redefined [no change]. (Calif. Stats. 1987–1988, reg. sess., ch. 363/p. 1676)
12 Feb 1874 SAN BENITO created from MONTEREY. (Calif. Stats. 1873, 20th sess., ch. 87/pp. 95–99)
11 Mar 1887 SAN BENITO gained from FRESNO and gained small area from MERCED. (Calif. Stats. 1887, 27th sess., ch. 86/p.103)
26 Apr 1853 SAN BERNARDINO created from LOS ANGELES. (Calif. Stats. 1853, 4th sess., ch. 78/pp. 119–123)
02 Apr 1857 SAN BERNARDINO boundaries redefined [no change]. (Calif. Stats. 1857, 8th sess., ch. 142/p. 165)
01 Jan 1873 SAN BERNARDINO gained from SAN DIEGO, lost to INYO. (Political Code 1872, 1: secs. 3942–3944/pp. 139–141)
05 Feb 1877 SAN BERNARDINO gained from LOS ANGELES as a result of an official survey of the boundary. (Coy, 149, 217–219)
02 May 1893 SAN BERNARDINO lost to creation of RIVERSIDE. Act passed 11 March 1893; referendum for or against creation of new county held 2 May 1893. (Calif. Stats. 1893, 30th sess., ch. 142/pp. 158–168)
27 Jul 1917 SAN BERNARDINO gained from KERN. (Calif. Stats. 1917, 42d sess., ch. 205/p. 301)
22 Jul 1919 SAN BERNARDINO exchanged with RIVERSIDE. (Calif. Stats. 1919, 43d sess., ch. 62/p. 99)
19 Sep 1947 Boundary between SAN BERNARDINO and INYO placed in dispute. Section 23136 of Political Code was revised to authorize SAN BERNARDINO to gain from INYO a strip of territory one and one-half miles wide between the San Bernardino Meridian and the state line. The companion description of INYO boundaries in section 23114 authorized no such change [no change]. (Calif. Stats. 1947, reg. sess., ch. 424, secs. 23114, 23136/pp. 1050, 1068)
11 Sep 1957 SAN BERNARDINO gained small area from INYO; boundaries of SAN BERNARDINO and INYO clarified, ending boundary dispute dating from 1947. (Calif. Stats. 1957, reg. sess., ch. 2382/p. 4119)
13 May 1963 SAN BERNARDINO exchanged small areas with KERN. (Coy, 340, 342; correspondence, California Board of Equalization, 25 July 2002)
11 Jul 1967 SAN BERNARDINO boundaries redefined to more precisely define the boundary between SAN BERNARDINO and the State of Arizona [exchange of territory too small to map]. (Calif. Stats. 1967, reg. sess., ch. 655/pp. 2024–2026; Coy, 341–342)
1972 In 1972, boundary between INYO and SAN BERNARDINO was adjusted [precise location unknown, not mapped]. (Correspondence, California State Board of Equalization, 25 July 2002)
01 Mar 1992 SAN BERNARDINO gained small area from LOS ANGELES. Ordinance passed 27 January 1992; effective 1 March 1992 [for location see 1992_pt.shp; change too small to display on interactive map]. (Minutes of the Board of Supervisors, San Bernardino County, 27 January 1992, ordinance 3478)
11 Oct 1993 SAN BERNARDINO gained small area from LOS ANGELES [for location see 1993_pt.shp; change too small to display on interactive map]. (Calif. Stats. 1993–1994, reg. sess., ch. 1195, sec. 3/p. 6854)
18 Feb 1850 SAN DIEGO created from non-county area. (Calif. Stats. 1849, 1st sess., ch. 15, sec. 2/pp. 58–59)
25 Apr 1851 SAN DIEGO exchanged with LOS ANGELES, lost to MARIPOSA. (Calif. Stats. 1851, 2d sess., ch. 14, sec. 2/p. 172)
30 Mar 1868 SAN DIEGO boundaries clarified [no change]. (Calif. Stats. 1867, 17th sess., ch. 453/p. 604)
01 Jan 1873 SAN DIEGO gained from LOS ANGELES, lost to SAN BERNARDINO. (Political Code 1872, 1: secs. 3943–3945/pp. 140–142)
02 May 1893 SAN DIEGO lost to creation of RIVERSIDE. Act passed 11 March 1893; referendum for or against creation of new county held 2 May 1893. (Calif. Stats. 1893, 30th sess., ch. 142/pp. 158–168)
12 Aug 1907 SAN DIEGO lost to creation of IMPERIAL. (Coy, 50–51; Farr, 18–19)
18 Feb 1850 SAN FRANCISCO created from non-county area; southern boundary with BRANCIFORTE (now SANTA CRUZ) was in dispute when the counties disagreed over the interpretation of the boundary description. (Calif. Stats. 1849, 1st sess., ch. 15, sec. 8/pp. 59–60; Stanger, 88)
05 Apr 1850 SAN FRANCISCO boundaries in San Francisco Bay clarified [no change]. (Calif. Stats. 1849, 1st sess., ch. 61, sec. 2/p. 156)
25 Apr 1851 SAN FRANCISCO boundaries redefined [no change]. (Calif. Stats. 1851, 2d sess., ch. 14, sec. 8/p. 174)
15 May 1854 SAN FRANCISCO lost "Island of Los Angeles" (Angel Island) in San Francisco Bay to MARIN. (Calif. Stats. 1854, 5th sess., ch. 67/p. 121)
01 Jul 1856 SAN FRANCISCO lost to creation of SAN MATEO. Act passed 19 April 1856; took effect 1 July 1856. (Calif. Stats. 1856, 7th sess., ch. 125/pp. 145–146, 176–178)
18 Apr 1857 SAN FRANCISCO gained Angel Island in San Francisco Bay from MARIN. Boundary between SAN FRANCISCO and SAN MATEO adjusted to run on public land survey line [no discernible change]. (Calif. Stats. 1857, 8th sess., chs. 190, 192/pp. 209–210, 222–223)
25 Apr 1860 SAN FRANCISCO lost Angel Island in San Francisco Bay to MARIN. (Calif. Stats. 1860, 11th sess., ch. 288/p. 269)
30 Mar 1874 SAN FRANCISCO lost small area in San Francisco Bay to ALAMEDA; placed all of the Central Pacific Railroad Wharf in ALAMEDA. The wharf was removed in 1919 [for location see 1874_pt.shp; change too small to display on interactive map]. (Calif. Stats. 1873, 20th sess., Acts Amendatory of the Codes, pp. 168–170; Coy, 62–63)
1949–1959 Between 1949 and 1959 (precise date unknown), SAN FRANCISCO gained a small area of the Alameda Naval Air Station when landfill expansion extended westward over the county line between SAN FRANCISCO and ALAMEDA in San Francisco Bay. (U.S.G.S., 7.5 Minute Series, Oakland West Quadrangle, "Edition of 1949" and "Edition of 1959")
18 Feb 1850 SAN JOAQUIN created from non-county area. (Calif. Stats. 1849, 1st sess., ch. 15, sec. 26/p. 63; Tinkham, 64)
25 Apr 1851 SAN JOAQUIN boundaries redefined [no change]. (Calif. Stats. 1851, 2d sess., ch. 14, sec. 12/p. 175)
14 Feb 1852 SAN JOAQUIN gained from CONTRA COSTA. (Calif. Stats. 1852, 3d sess., chs. 105–106/pp. 178–180; Purcell, 250)
17 Feb 1860 SAN JOAQUIN lost to STANISLAUS. (Calif. Stats. 1860, 11th sess., ch. 62/pp. 34–35)
23 Apr 1861 SAN JOAQUIN lost to SACRAMENTO. (Calif. Stats. 1861, 12th sess., ch. 219/p. 221; Tinkham, 64–65)
01 Apr 1878 SAN JOAQUIN gained from SACRAMENTO. (Calif. Stats. 1877, 22d sess., Acts Amendatory of the Political Code, ch. 636/p. 70)
18 Mar 1905 Boundary between SAN JOAQUIN and SACRAMENTO redefined [no change]. (Calif. Stats. 1905, 36th sess., ch. 167/p. 164)
18 Feb 1850 SAN LUIS OBISPO created from non-county area. (Calif. Stats. 1849, 1st sess., ch. 15, sec. 5/p. 59)
25 Apr 1851 SAN LUIS OBISPO gained from SANTA BARBARA, exchanged with MONTEREY. (Calif. Stats. 1851, 2d sess., ch. 14, sec. 5/p. 173)
24 Apr 1852 SAN LUIS OBISPO lost to SANTA BARBARA. (Calif. Stats. 1852, 3d sess., ch. 133/p. 218)
13 May 1854 SAN LUIS OBISPO exchanged with SANTA BARBARA. (Calif. Stats. 1854, 5th sess., ch. 24/p. 148)
13 May 1861 SAN LUIS OBISPO gained from MONTEREY. (Calif. Stats. 1861, 12th sess., ch. 342/p. 349)
20 Apr 1863 SAN LUIS OBISPO lost to MONTEREY. (Calif. Stats. 1863, 14th sess., ch. 276/p. 358)
01 Jan 1873 SAN LUIS OBISPO exchanged with SANTA BARBARA, lost to creation of VENTURA. (Calif. Stats. 1871, 19th sess., ch. 351/pp. 484–489; Political Code 1872, 1: secs. 3946–3947/pp. 142–143)
14 Mar 1885 SAN LUIS OBISPO exchanged with KERN. (Calif. Stats. 1885, 26th sess., ch. 149/pp. 139–141)
02 May 1991 SAN LUIS OBISPO lost small area to SANTA BARBARA [for location see 1991_pt.shp; change too small to display on interactive map]. (Leaha K. Magee, San Luis Obispo County LAFCO, correspondence, 29 October 2002)
09 Jul 1992 SAN LUIS OBISPO lost small area to SANTA BARBARA [for location see 1992_pt.shp; change too small to display on interactive map]. (Leaha K. Magee, San Luis Obispo County LAFCO, correspondence, 29 October 2002)
01 Jul 1856 SAN MATEO created from SAN FRANCISCO; southern boundary with SANTA CRUZ was in dispute [see 18 February 1850]. Act passed 19 April 1856; took effect 1 July 1856. (Calif. Stats. 1856, 7th sess., ch. 125/pp. 145–146, 176–178)
18 Apr 1857 Boundary between SAN FRANCISCO and SAN MATEO adjusted to run on public land survey line [no discernible change]. SAN MATEO boundaries clarified, ending dispute with SANTA CRUZ; gave SAN MATEO control over area disputed with SANTA CRUZ. (Calif. Stats. 1857, 8th sess., chs. 190, 192/pp. 209–210, 222–223; Stanger, 88)
16 Mar 1868 SAN MATEO gained from SANTA CRUZ. (Calif. Stats. 1867, 17th sess., ch. 195/p. 174)
14 Mar 1878 Boundary between SAN MATEO and ALAMEDA in San Francisco Bay was adjusted [not mapped]. (Calif. Stats. 1877, 22d sess., Acts Amendatory of the Political Code, ch. 197/p. 71)
14 Mar 1901 SAN MATEO boundaries clarified [no change]. (Calif. Stats. 1901, 34th sess., ch. 128/p. 291)
14 Oct 1963 SAN MATEO lost small area to SANTA CLARA [for location see 1963_pt.shp; change too small to display on interactive map]. (Coy, 342–343, 345)
11 Jul 1968 SAN MATEO boundaries clarified [no change]. (Calif. Stats. 1968, reg. sess., ch. 537, sec. 1/pp. 1189–1191)
18 Feb 1850 SANTA BARBARA created from non-county area. (Calif. Stats. 1849, 1st sess., ch. 15, sec. 4/p. 59)
25 Apr 1851 SANTA BARBARA exchanged with LOS ANGELES, lost to SAN LUIS OBISPO. (Calif. Stats. 1851, 2d sess., ch. 14, sec. 4/p. 173)
24 Apr 1852 SANTA BARBARA gained from SAN LUIS OBISPO. (Calif. Stats. 1852, 3d sess., ch. 133/p. 218)
13 May 1854 SANTA BARBARA exchanged with SAN LUIS OBISPO. (Calif. Stats. 1854, 5th sess., ch. 24/p. 148)
01 Jan 1873 SANTA BARBARA exchanged with SAN LUIS OBISPO, lost to creation of VENTURA. (Calif. Stats. 1871, 19th sess., ch. 351/pp. 484–489; Political Code 1872, 1: secs. 3946–3947/pp. 142–143)
05 Jun 1968 SANTA BARBARA boundaries redefined to correct mistake in Government Political Code. The word "northwest" was replaced by "southwestern" [no change]. (Calif. Stats. 1968, reg. sess., ch. 248/p. 561)
02 May 1991 SANTA BARBARA gained small area from SAN LUIS OBISPO [for location see 1991_pt.shp; change too small to display on interactive map]. (Leaha K. Magee, San Luis Obispo County LAFCO, correspondence, 29 October 2002)
09 Jul 1992 SANTA BARBARA gained small area from SAN LUIS OBISPO [for location see 1992_pt.shp; change too small to display on interactive map]. (Leaha K. Magee, San Luis Obispo County LAFCO, correspondence, 29 October 2002)
18 Feb 1850 SANTA CLARA created from non-county area. (Calif. Stats. 1849, 1st sess., ch. 15, sec. 9/p. 60)
05 Apr 1850 SANTA CLARA boundaries clarified [no change]. (Calif. Stats. 1849, 1st sess., ch. 61, sec. 3/p. 156)
25 Apr 1851 SANTA CLARA boundaries redefined [no change]. (Calif. Stats. 1851, 2d sess., ch. 14, sec. 9/p. 174)
25 Mar 1853 SANTA CLARA gained small remnant from CONTRA COSTA, lost to creation of ALAMEDA. (Calif. Stats. 1853, 4th sess., ch. 41/pp. 56–59)
14 Oct 1963 SANTA CLARA gained small area from SAN MATEO [for location see 1963_pt.shp; change too small to display on interactive map]. (Coy, 342–343, 345)
11 Jul 1968 SANTA CLARA boundaries clarified [no change]. (Calif. Stats. 1968, reg. sess., ch. 537, sec. 2/pp. 1191–1193)
02 Nov 1971 SANTA CLARA gained small areas from ALAMEDA [for location see 1971_pt.shp; change too small to display on interactive map]. (Coy, 338, 343)
17 Nov 1971 SANTA CLARA exchanged small areas with SANTA CRUZ as the boundary was clarified along its entire length [not mapped]. (Coy, 343–345)
07 Apr 1976 SANTA CLARA boundaries clarified [no change]. (Calif. Stats. 1976, reg. sess., ch. 102, sec. 1/pp. 161–162)
11 Dec 1998 SANTA CLARA gained small area from SANTA CRUZ [precise location unknown, not mapped]. (Correspondence, California State Board of Equalization, 25 July 2002)
18 Feb 1850 BRANCIFORTE (now SANTA CRUZ) created from non-county area; northern boundary with SAN FRANCISCO was in dispute when the counties disagreed over the interpretation of the boundary description. (Calif. Stats. 1849, 1st sess., ch. 15, sec. 7/p. 59; Stanger, 88)
05 Apr 1850 BRANCIFORTE renamed SANTA CRUZ; boundaries redefined [no change]. (Calif. Stats. 1849, 1st sess., ch. 61, sec. 1/pp. 155–156)
25 Apr 1851 SANTA CRUZ boundaries redefined [no change]. (Calif. Stats. 1851, 2d sess., ch. 14, sec. 7/p. 173)
01 Jul 1856 SAN MATEO created from SAN FRANCISCO; SAN MATEO boundary with SANTA CRUZ was in dispute [see 18 February 1850]. (Calif. Stats. 1856, 7th sess., ch. 125/pp. 145–146, 176–178)
18 Apr 1857 SAN MATEO boundaries clarified, ending dispute with SANTA CRUZ; SANTA CRUZ lost control of area disputed with SAN MATEO. (Calif. Stats. 1857, 8th sess., ch. 192/pp. 222–223; Stanger, 88)
16 Mar 1868 SANTA CRUZ lost to SAN MATEO. (Calif. Stats. 1867, 17th sess., ch. 195/p. 174)
17 Nov 1971 SANTA CRUZ exchanged small areas with SANTA CLARA as the boundary was clarified along its entire length [not mapped]. (Coy, 343–345)
07 Apr 1976 SANTA CRUZ boundaries clarified [no change]. (Calif. Stats. 1976, reg. sess., ch. 102, sec. 2/pp. 162–165)
11 Dec 1998 SANTA CRUZ lost small area to SANTA CLARA [precise location unknown, not mapped]. (Correspondence, California State Board of Equalization, 25 July 2002)
18 Feb 1850 SHASTA created from non-county area. TRINITY not fully organized, attached to SHASTA for judicial and other purposes. (Calif. Stats. 1849, 1st sess., ch. 15, sec. 23/p. 62)
25 Apr 1851 SHASTA gained from COLUSI (now COLUSA), and gained small area from BUTTE. (Calif. Stats. 1851, 2d sess., ch. 14, sec. 22/p. 177)
09 Jun 1851 TRINITY fully organized; detached from SHASTA. (Calif. Stats. 1851, 2d sess., ch. 132/pp. 516–518; Cox, 116–117)
22 Mar 1852 SHASTA lost to creation of SISKIYOU. (Calif. Stats. 1852, 3d sess., ch. 146/pp. 233–235)
24 Apr 1852 SHASTA boundaries redefined [no change]. (Calif. Stats. 1852, 3d sess., ch. 142/p. 228)
09 Apr 1856 SHASTA lost to creation of TEHAMA. (Calif. Stats. 1856, 7th sess., ch. 100/pp. 118–119)
21 Apr 1856 SHASTA exchanged with TEHAMA. (Calif. Stats. 1856, 7th sess., ch. 141/p. 222)
19 Feb 1857 SHASTA exchanged with TEHAMA. (Calif. Stats. 1857, 8th sess., ch. 37/p. 25)
01 Apr 1864 SHASTA lost to creation of LASSEN. (Calif. Stats. 1863–1864, 15th sess., ch. 261/pp. 264–269)
01 Jan 1873 SHASTA gained from PLUMAS. (Political Code 1872, 1: secs. 3911, 3915, 3920/pp. 115, 118, 122–123)
14 Mar 1899 SHASTA lost to LASSEN. (Calif. Stats. 1899, 33d sess., ch. 82/p. 98)
23 Mar 1901 Boundary between SHASTA and PLUMAS clarified to run on public land survey line [no discernible change]. (Calif. Stats. 1901, 34th sess., ch. 171/p. 560)
16 Apr 1852 SIERRA created from YUBA. (Calif. Stats. 1852, 3d sess., ch. 145/pp. 230–231)
03 May 1852 SIERRA lost to NEVADA. (Calif. Stats. 1852, 3d sess., chs. 114–115/pp. 190–192)
19 Apr 1856 SIERRA lost to NEVADA. (Calif. Stats. 1856, 7th sess., ch. 122/p. 143)
27 Mar 1863 SIERRA gained from PLUMAS. (Calif. Stats. 1863, 14th sess., ch. 101/p. 114; Sinnott, 6:19–22)
13 Mar 1866 SIERRA gained from YUBA. (Calif. Stats. 1865, 16th sess., ch. 229/p. 228)
31 Mar 1866 SIERRA lost to PLUMAS. (Calif. Stats. 1865, 16th sess., ch. 466/p. 605)
28 Mar 1868 SIERRA gained small area from PLUMAS. (Calif. Stats. 1867, 17th sess., ch. 377/p. 462)
16 Mar 1874 SIERRA gained from LASSEN and PLUMAS when boundary was set on public land survey lines. (Calif. Stats. 1873, 20th sess., Acts Amendatory of the Codes, p. 166)
28 Dec 1908 California Supreme Court settled boundary dispute between SIERRA and NEVADA in favor of SIERRA. Dispute grew out of disagreement over the location of the source of the South Fork of Middle Yuba River [no change]. ("Sierra County v. Nevada County," in Calif. Rpts., 155:1–15)
01 Mar 1909 SIERRA boundaries clarified [no change]. (Calif. Stats. 1909, 38th sess., ch. 75, sec. 1/p. 86)
22 Mar 1852 SISKIYOU created from KLAMATH (extinct) and SHASTA. (Calif. Stats. 1852, 3d sess., ch. 146/pp. 233–235)
02 Mar 1857 SISKIYOU lost small area to creation of DEL NORTE. (Calif. Stats. 1857, 8th sess., ch. 52/pp. 35–36)
01 Jan 1873 SISKIYOU exchanged with DEL NORTE. (Political Code 1872, 1:secs. 3909, 3913/pp. 113–114, 117)
17 Feb 1874 SISKIYOU lost to creation of MODOC. (Calif. Stats. 1873, 20th sess., ch. 107/pp. 124–129)
30 May 1874 SISKIYOU gained part of KLAMATH; KLAMATH eliminated. Act passed 28 March 1874; referendum for annexation of KLAMATH held 30 May 1874. (Calif. Stats. 1873, 20th sess., ch. 520/pp. 755–758; Kasch, 270–272)
11 Mar 1887 SISKIYOU exchanged with DEL NORTE. (Calif. Stats. 1887, 27th sess., ch. 88/pp. 105–107)
23 Mar 1901 SISKIYOU gained small area from HUMBOLDT. (Calif. Stats. 1901, 34th sess., ch. 193/p. 600)
18 Feb 1850 SOLANO created from non-county area. (Calif. Stats. 1849, 1st sess., ch. 15, sec. 13/p. 61)
25 Apr 1851 SOLANO boundaries redefined [no change]. (Calif. Stats. 1851, 2d sess., ch. 14, sec. 27/p. 179)
27 Jan 1853 SOLANO gained Mare Island, a non-county area that had been part of SONOMA until 3 May 1852. (Calif. Stats. 1853, 4th sess., ch. 5/p. 20)
04 Apr 1855 SOLANO lost to NAPA. (Calif. Stats. 1855, 6th sess., ch. 68/p. 77)
27 Apr 1855 SOLANO gained from SONOMA. (Calif. Stats. 1855, 6th sess., ch. 125/p. 150)
26 Mar 1857 SOLANO lost to YOLO. (Calif. Stats. 1857, 8th sess., ch. 104/p. 108)
12 Mar 1870 SOLANO lost small area to SACRAMENTO. (Calif. Stats. 1869, 18th sess., ch. 191/p. 294)
01 Jan 1980 SOLANO lost small area to YOLO. Ordinance passed 20 November 1979; effective 1 January 1980 [for location see 1980_pt.shp; change too small to display on interactive map]. (Minutes of the Board of Supervisors, Solano County, 20 November 1979, ordinance 1085; Minutes of the Board of Supervisors, Yolo County, 20 November 1979, ordinance 861)
18 Dec 1992 SOLANO lost small area to YOLO [for location see 1992_pt.shp; change too small to display on interactive map]. (Minutes of the Board of Supervisors, Solano County, 8 December 1992, ordinance 1460; Minutes of the Board of Supervisors, Yolo County, 24 November 1992, ordinance 1153)
18 Feb 1850 SONOMA created from non-county area. MARIN and MENDOCINO not fully organized, attached to SONOMA "for judicial purposes." (Calif. Stats. 1849, 1st sess., ch. 15, sec. 12/p. 60)
22 Apr 1850 MARIN fully organized, detached from SONOMA. MENDOCINO remained attached to SONOMA. (Calif. Stats. 1849, 1st sess., ch. 131/p. 406)
25 Apr 1851 SONOMA boundaries redefined [no change]. (Calif. Stats. 1851, 2d sess., ch. 14, sec. 24/p. 178)
03 May 1852 SONOMA lost Mare Island when SONOMA boundaries were redefined. Mare Island remained a non-county area until 27 January 1853 when it became part of SOLANO. (Calif. Stats. 1852, 3d sess., ch. 147/p. 236)
04 Apr 1855 SONOMA lost to NAPA. (Calif. Stats. 1855, 6th sess., ch. 68/p. 77)
27 Apr 1855 SONOMA gained from MARIN, exchanged with MENDOCINO, lost to SOLANO. (Calif. Stats. 1855, 6th sess., ch. 125/p. 150)
11 Mar 1859 SONOMA exchanged with MENDOCINO. (Calif. Stats. 1859, 10th sess., ch. 108/pp. 98–99)
02 May 1859 MENDOCINO fully organized, detached from SONOMA. (Calif. Stats. 1859, 10th sess., ch. 108, sec. 2/p. 99; History of Mendocino County, 272–273, 283)
25 Apr 1860 SONOMA lost to MARIN when boundary was changed to run on road [see 13 May 1861]. (Calif. Stats. 1860, 11th sess., ch. 288/p. 269)
13 May 1861 SONOMA gained from MARIN [repealed part of act of 25 April 1860]. (Calif. Stats. 1861, 12th sess., ch. 346/p. 351)
10 Feb 1868 SONOMA boundaries redefined [no change]. (Calif. Stats. 1867, 17th sess., ch. 45/p. 42)
30 Jul 1917 SONOMA exchanged with MENDOCINO. (Calif. Stats. 1917, 42d sess., ch. 725/p. 1396)
05 Apr 1854 STANISLAUS created from TUOLUMNE. (Calif. Stats. 1854, 5th sess., chs. 35, 81/pp. 40–41, 191–194)
04 May 1855 Boundary between STANISLAUS and TUOLUMNE clarified [no change]. (Calif. Stats. 1855, 6th sess., ch. 194/p. 245)
17 Feb 1860 STANISLAUS gained from SAN JOAQUIN. (Calif. Stats. 1860, 11th sess., ch. 62/pp. 34–35)
08 Mar 1866 Legislature authorized a re-survey of the STANISLAUS-MERCED line, established in 1854, which would have resulted in STANISLAUS losing to MERCED. Loss did not take effect; see 13 February 1868. [Proposed change not displayed on interactive map; see "Special Topics."] (Calif. Stats. 1865, 16th sess., ch. 191/p. 172; Outcalt, 118–119, 122–123)
13 Feb 1868 Boundary between STANISLAUS and MERCED redefined to confirm 1854 STANISLAUS line; see 8 March 1866 [no change]. (Calif. Stats. 1867, 17th sess., ch. 57/p. 56)
02 Jul 1986 STANISLAUS boundaries clarified [no change]. (Calif. Stats. 1985–1986, reg. sess., ch. 248, sec. 80/p. 1239)
18 Feb 1850 SUTTER created from non-county area. (Calif. Stats. 1849, 1st sess., ch. 15, sec. 19/p. 62)
25 Apr 1851 SUTTER gained from YUBA, lost to BUTTE, and lost to creation of PLACER. (Calif. Stats. 1851, 2d sess., ch. 14, secs. 17–18/p. 176)
03 May 1852 SUTTER exchanged with BUTTE. (Calif. Stats. 1852, 3d sess., ch. 149/p. 237)
31 Mar 1854 SUTTER gained from BUTTE. (Calif. Stats. 1854, 5th sess., ch. 16/p. 26)
19 Apr 1856 SUTTER lost to COLUSI (now COLUSA). (Calif. Stats. 1856, 7th sess., ch. 105/p. 124)
21 Apr 1856 SUTTER gained from BUTTE. (Calif. Stats. 1856, 7th sess., ch. 150/p. 231)
01 Apr 1864 SUTTER gained from BUTTE. (Calif. Stats. 1863–1864, 15th sess., ch. 292/p. 301)
13 Mar 1866 SUTTER exchanged with PLACER. (Calif. Stats. 1865, 16th sess., ch. 224/p. 223)
01 Jan 1873 SUTTER lost small area to PLACER. (Political Code 1872, 1: secs. 3924, 3926/pp. 125–127)
31 Mar 1891 SUTTER gained small area from COLUSA [for location see 1891_pt.shp; change too small to display on interactive map]. (Calif. Stats. 1891, 29th sess., ch. 240/p. 455)
09 Sep 1953 SUTTER exchanged with YUBA along Bear River. (Calif. Stats. 1953, reg. sess., ch. 836, sec. 1/pp. 2148–2152)
28 Mar 1994 SUTTER lost small area to YUBA [for location see 1994_pt.shp; change too small to display on interactive map]. (Minutes of the Board of Supervisors, Yuba County, 20 July 1993, ordinance 1140)
09 Apr 1856 TEHAMA created from BUTTE, COLUSI (now COLUSA), and SHASTA. (Calif. Stats. 1856, 7th sess., ch. 100/pp. 118–119)
21 Apr 1856 TEHAMA exchanged with SHASTA. (Calif. Stats. 1856, 7th sess., ch. 141/p. 222)
19 Feb 1857 TEHAMA exchanged with SHASTA, lost to COLUSI (now COLUSA). (Calif. Stats. 1857, 8th sess., ch. 37/p. 25)
26 Mar 1857 TEHAMA boundaries redefined [no change]. (Calif. Stats. 1857, 8th sess., ch. 105/p. 109)
19 Apr 1859 TEHAMA gained from COLUSA, lost to BUTTE. (Calif. Stats. 1859, 10th sess., ch. 322/p. 359)
01 Jan 1873 TEHAMA lost to COLUSA. (Political Code 1872, 1: secs. 3915–3916/pp. 118–119)
20 Nov 1944 TEHAMA exchanged with BUTTE. (Coy, 339, 345)
18 Feb 1850 TRINITY created from non-county area; TRINITY not fully organized, attached to SHASTA for judicial and other purposes. (Calif. Stats. 1849, 1st sess., ch. 15, sec. 24/p. 62)
25 Apr 1851 TRINITY lost to creation of KLAMATH (extinct). (Calif. Stats. 1851, 2d sess., ch. 14, secs. 30–31/pp. 179–180)
09 Jun 1851 TRINITY fully organized; detached from SHASTA. (Calif. Stats. 1851, 2d sess., ch. 132/pp. 516–518; Cox, 116–117)
12 May 1853 TRINITY lost to creation of HUMBOLDT. (Calif. Stats. 1853, 4th sess., ch. 114/pp. 161–164)
30 Apr 1855 TRINITY gained from KLAMATH (extinct). (Calif. Stats. 1855, 6th sess., ch. 156/p. 200)
11 Mar 1859 TRINITY lost to MENDOCINO. (Calif. Stats. 1859, 10th sess., ch. 108/pp. 98–99)
28 Apr 1860 TRINITY gained from MENDOCINO. (Calif. Stats. 1860, 11th sess., ch. 340/p. 334)
30 Oct 1872 TRINITY gained from MENDOCINO when their common boundary was surveyed; later MENDOCINO claimed a different boundary based on an 1891 survey. California Supreme Court upheld 1872 survey on 15 May 1907. (Calif. Stats. 1871, 19th sess., ch. 531/p. 766; "Trinity County v. Mendocino County," in Calif. Rpts., 151: 279–289)
20 Apr 1852 TULARE created from MARIPOSA. (Calif. Stats. 1852, 3d sess., ch. 153/pp. 240–242)
30 Apr 1855 Legislature authorized creation of BUENA VISTA (proposed) from TULARE; creation did not take effect. (Calif. Stats. 1855, 6th sess., ch. 161/pp. 203–205; Coy, 15–16)
16 Apr 1856 Legislature authorized TULARE to lose to BUENA VISTA (proposed), even though the creation of BUENA VISTA (authorized 30 April 1855) had never gone into effect. [Proposed change not displayed on interactive map; see "Special Topics."] (Calif. Stats. 1856, 7th sess., ch. 81/p. 96)
19 Apr 1856 TULARE lost to creation of FREZNO (now FRESNO), gained from MERCED. (Calif. Stats. 1856, 7th sess., ch. 127/pp. 183)
04 Apr 1864 Legislature authorized creation of COSO from MONO and TULARE; creation did not take effect [see creation of INYO, 22 March 1866]. (Calif. Stats. 1863–1864, 15th sess., ch. 470/pp. 528–530)
22 Mar 1866 TULARE lost to creation of INYO; INYO boundaries were identical to those of COSO (proposed) [see 4 April 1864]. (Calif. Stats. 1865, 16th sess., ch. 316/pp. 355–358)
02 Apr 1866 TULARE lost to creation of KERN. (Calif. Stats. 1865, 16th sess., ch. 569/pp. 796–798)
10 Feb 1868 TULARE lost to KERN. (Calif. Stats. 1867, 17th sess., ch. 43/p. 40)
22 Jan 1870 TULARE lost to MONO the remnant of territory that was separated from TULARE by the creation of INYO on 22 March 1866. (Calif. Stats. 1869, 18th sess., ch. 18/p. 20)
01 Jan 1873 TULARE gained from KERN. (Political Code 1872, 1: secs. 3940–3941/pp. 138–139)
27 Mar 1874 TULARE exchanged with FRESNO. (Calif. Stats. 1873, 20th sess., ch. 468/p. 700)
23 Mar 1876 TULARE exchanged with FRESNO. (Calif. Stats. 1875, 21st sess., ch. 301/p. 397)
23 May 1893 TULARE lost to creation of KINGS. Act passed 22 March 1893; referendum for or against creation of new county held 23 May 1893. (Calif. Stats. 1893, 30th sess., ch. 150/pp. 176–181; Kings County History, http://calflytech.com/kingshistory.html, 18 July 2002)
31 Dec 1986 TULARE lost small area to FRESNO. Ordinance passed 18 November 1986; effective 31 December 1986 [for location see 1986_pt.shp; change too small to display on interactive map]. (Minutes of the Board of Supervisors, Tulare County, 18 November 1986, ordinance 2745)
30 Sep 1991 TULARE exchanged small areas with FRESNO. Ordinance passed 3 September 1991; effective 30 September 1991 [for location see 1991_pt.shp; change too small to display on interactive map]. (Minutes of the Board of Supervisors, Tulare County, 3 September 1991, ordinance 2970)
18 Feb 1850 TUOLUMNE created from non-county area. (Calif. Stats. 1849, 1st sess., ch. 15, sec. 27/p. 63)
18 Apr 1850 TUOLUMNE boundaries clarified [no change]. (Calif. Stats. 1849, 1st sess., ch. 111/pp. 262–263)
25 Apr 1851 TUOLUMNE boundaries redefined [no change]. (Calif. Stats. 1851, 2d sess., ch. 14, sec. 14/p. 175)
05 Apr 1854 TUOLUMNE lost to creation of STANISLAUS. (Calif. Stats. 1854, 5th sess., chs. 35, 81/pp. 40–41, 191–194)
04 May 1855 Boundary between TUOLUMNE and STANISLAUS clarified [no change]. (Calif. Stats. 1855, 6th sess., ch. 194/p. 245)
19 Apr 1856 TUOLUMNE lost to creation of FREZNO (now FRESNO). (Calif. Stats. 1856, 7th sess., ch. 127/pp. 183)
11 Apr 1859 TUOLUMNE gained from FREZNO (now FRESNO). (Calif. Stats. 1859, 10th sess., ch. 204/p. 213)
16 Mar 1864 TUOLUMNE lost to creation of ALPINE. (Calif. Stats. 1863–1864, 15th sess., ch. 180/pp. 178–182)
01 Jan 1873 VENTURA created from SAN LUIS OBISPO and SANTA BARBARA. Act passed 22 March 1872; took effect 1 January 1873. (Calif. Stats. 1871, 19th sess., ch. 351/pp. 484–489; Political Code 1872, 1: secs. 3946–3947/pp. 142–143)
Jul 1881 In July 1881, VENTURA gained from LOS ANGELES as a result of an official boundary survey. (Coy, 150–154, 292)
23 Jul 1919 VENTURA lost to KERN when boundary was adjusted to run on public land survey lines; legislature authorized VENTURA to exchange with LOS ANGELES. The California Supreme Court declared this chapter of the 1919 Political Code unconstitutional on 19 February 1920, but the VENTURA/KERN change appears to have remained in effect; change confirmed in 1923 by reenactment of the 1919 law. [Proposed change not displayed on interactive map; see "Special Topics."] (Calif. Stats. 1919, 43d sess., ch. 470, secs. 3923, 3964/pp. 870, 908–909; "Mundell v. Lyons," in Calif. Rpts., 182:289–293; Calif. Laws 1923, 45th sess., ch. 160, secs. 16, 57/pp. 336, 373; Coy, 152-153)
16 May 1923 VENTURA boundaries redefined; see 23 July 1919 [no change]. (Calif. Laws 1923, 45th sess., ch. 160, secs. 16, 57/pp. 336, 373)
31 Dec 1986 VENTURA lost small area to KERN [precise location unknown, not mapped]. (Minutes of the Board of Supervisors, Kern County, 4 November 1986, ordinance G–4345)
10 Jun 1991 VENTURA lost to KERN. (Calif. Stats. 1991–1992, reg. sess., ch. 51/p. 150)
18 Feb 1850 YOLO created from non-county area. County was named "YOLA" in this act; by April 1850 the current spelling was in use. (Calif. Stats. 1849, 1st sess., ch. 15, sec. 14/p. 61)
05 Apr 1850 YOLO boundaries clarified [no change]. (Calif. Stats. 1849, 1st sess., ch. 61, sec. 5/p. 156)
25 Apr 1851 YOLO lost to COLUSI (now COLUSA). (Calif. Stats. 1851, 2d sess., ch. 14, sec. 28/p. 179)
19 Apr 1856 YOLO lost to COLUSI (now COLUSA). (Calif. Stats. 1856, 7th sess., ch. 105/p. 124)
26 Mar 1857 YOLO gained from SOLANO. (Calif. Stats. 1857, 8th sess., ch. 104/p. 108)
03 Mar 1866 YOLO boundaries clarified [no change]. (Calif. Stats. 1865, 16th sess., ch. 181/p. 162; "Waters v. Pool," in Calif. Rpts., 130:136–139)
24 Mar 1868 YOLO lost to LAKE. (Calif. Stats. 1867, 17th sess., ch. 257/p. 269)
12 Mar 1870 YOLO lost small area to SACRAMENTO. (Calif. Stats. 1869, 18th sess., ch. 191/p. 294)
01 Jan 1980 YOLO gained small area from SOLANO. Ordinance passed 20 November 1979; effective 1 January 1980 [for location see 1980_pt.shp; change too small to display on interactive map]. (Minutes of the Board of Supervisors, Solano County, 20 November 1979, ordinance 1085; Minutes of the Board of Supervisors, Yolo County, 20 November 1979, ordinance 861)
18 Dec 1992 YOLO gained small area from SOLANO [for location see 1992_pt.shp; change too small to display on interactive map]. (Minutes of the Board of Supervisors, Solano County, 8 December 1992, ordinance 1460; Minutes of the Board of Supervisors, Yolo County, 24 November 1992, ordinance 1153)
18 Feb 1850 YUBA created from non-county area. (Calif. Stats. 1849, 1st sess., ch. 15, sec. 20/p. 62)
25 Apr 1851 YUBA lost to SUTTER, and lost to creation of NEVADA and PLACER. (Calif. Stats. 1851, 2d sess., ch. 14, secs. 17, 19–20/pp. 176–177)
16 Apr 1852 YUBA lost to creation of SIERRA. (Calif. Stats. 1852, 3d sess., ch. 145/pp. 230–233)
22 Mar 1860 YUBA gained small area in village of Strawberry Valley from BUTTE [for location see 1860_pt.shp; change too small to display on interactive map]. (Calif. Stats. 1860, 11th sess., ch. 145/p. 115)
15 Apr 1861 YUBA gained small area at Woodville from BUTTE [for location see 1861_pt.shp; change too small to display on interactive map]. (Calif. Stats. 1861, 12th sess., ch. 166/p. 167)
13 Mar 1866 YUBA lost to SIERRA. (Calif. Stats. 1865, 16th sess., ch. 229/p. 228)
31 Mar 1866 YUBA lost small area to PLUMAS. (Calif. Stats. 1865, 16th sess., ch. 466/p. 605)
25 Feb 1897 YUBA exchanged with BUTTE. (Calif. Stats. 1897, 32d sess., ch. 26/p. 22)
09 Sep 1953 YUBA exchanged with SUTTER along Bear River. (Calif. Stats. 1953, reg. sess., ch. 836, sec. 2/pp. 2152–2156)
28 Mar 1994 YUBA gained small area from SUTTER [for location see 1994_pt.shp; change too small to display on interactive map]. (Minutes of the Board of Supervisors, Yuba County, 20 July 1993, ordinance 1140)