California: Consolidated Chronology of State and County Boundaries

California Atlas of Historical County Boundaries

John H. Long, Editor; Peggy Tuck Sinko, Historical Compiler; Laura Rico-Beck, GIS Specialst and Digital Compiler; Peter Siczewicz, ArcIMS Interactive Map Designer; Emily Kelley, Research Associate; Robert Will, Cartographic Assistant

Copyright The Newberry Library 2003

1769

Following years of exploration, Spain began colonizing and establishing control of Upper and Lower California. (Bancroft, 18:110–163; Rolle, 59–71)

29 September 1822

Mexico officially gained control of California, following Mexican independence from Spain in August 1821. (Beers, 203–204)

4 July 1848

Treaty of Guadalupe-Hidalgo ended the Mexican War between the United States and Mexico; Mexico ceded California to the United States. Treaty was signed 2 February 1848, proclaimed 4 July 1848. (Parry, 102:29–59; U.S. Stat., vol. 9, pp. 922–943; Van Zandt, 151)

1 September 1849

Delegates gathered in Monterey to draft a new California state constitution. The constitution was ratified 13 November 1849. (Swinder, 1:446–462)

15 December 1849

First session of the California legislature convened in San Jose. (Calif. Stats. 1849, 1st sess., title page)

18 February 1850

California legislature passed a single act creating twenty-seven new counties covering all of the state and leaving no part of California outside of county jurisdiction. New counties:

5 April 1850

BRANCIFORTE renamed SANTA CRUZ; boundaries redefined [no change]. (Calif. Stats. 1849, 1st sess., ch. 61, sec. 1/pp. 155–156)

CONTRA COSTA, SANTA CLARA, and YOLO boundaries clarified [no change]. (Calif. Stats. 1849, 1st sess., ch. 61, secs. 3–5/p. 156)

SAN FRANCISCO boundaries in San Francisco Bay clarified [no change]. (Calif. Stats. 1849, 1st sess., ch. 61, sec. 2/p. 156)

18 April 1850

CALAVERAS and TUOLUMNE boundaries clarified [no change]. (Calif. Stats. 1849, 1st sess., ch. 111/pp. 262–263)

22 April 1850

MARIN fully organized, detached from SONOMA. (Calif. Stats. 1849, 1st sess., ch. 131/p. 406)

9 September 1850

Congress admitted California to the Union as a state. (U.S. Stat., vol. 9, ch. 50[1850], pp. 452–453; Van Zandt, 151)

10 January 1851

COLUSI (now COLUSA) fully organized, detached from BUTTE. (Rogers, 57–61)

25 April 1851

Legislature redefined boundaries of CALAVERAS, CONTRA COSTA, EL DORADO, MARIN, MENDOCINO, NAPA, SACRAMENTO, SAN FRANCISCO, SAN JOAQUIN, SANTA CLARA, SANTA CRUZ, SOLANO, SONOMA, and TUOLUMNE [no changes]. (Calif. Stats. 1851, 2d sess., ch. 14, secs. 7–14, 16, 23–27/pp. 173–179)

COLUSI (now COLUSA) gained from YOLO. (Calif. Stats. 1851, 2d sess., ch. 14, secs. 28–29/p. 179)

KLAMATH (extinct) created from TRINITY. (Calif. Stats. 1851, 2d sess., ch. 14, secs. 30–31/pp. 179–180)

LOS ANGELES gained from MARIPOSA, exchanged with SAN DIEGO and SANTA BARBARA. (Calif. Stats. 1851, 2d sess., ch. 14, secs. 2–4, 15/pp. 172–173, 175–176)

MARIPOSA gained from SAN DIEGO. (Calif. Stats. 1851, 2d sess., ch. 14, secs. 2, 15/pp. 172, 175–176)

NEVADA created from YUBA. (Calif. Stats. 1851, 2d sess., ch. 14, sec. 20/p. 177)

PLACER created from SUTTER and YUBA. (Calif. Stats. 1851, 2d sess., ch. 14, sec. 17/p. 176)

SAN LUIS OBISPO gained from SANTA BARBARA, exchanged with MONTEREY. (Calif. Stats. 1851, 2d sess., ch. 14, secs.4–6/p. 173)

SHASTA gained from COLUSI (now COLUSA), and gained small area from BUTTE. (Calif. Stats. 1851, 2d sess., ch. 14, secs. 21–22, 29/pp. 177, 179)

SUTTER gained from YUBA, lost to BUTTE. (Calif. Stats. 1851, 2d sess., ch. 14, secs. 18–19, 21/pp. 176–177)

9 June 1851

TRINITY fully organized; detached from SHASTA. (Calif. Stats. 1851, 2d sess., ch. 132/pp. 516–518; Cox, 116–117)

14 February 1852

SAN JOAQUIN gained from CONTRA COSTA. (Calif. Stats. 1852, 3d sess., chs. 105–106/pp. 178–180; Purcell, 250)

22 March 1852

SISKIYOU created from KLAMATH (extinct) and SHASTA. (Calif. Stats. 1852, 3d sess., ch. 146/pp. 233–235)

16 April 1852

NAPA gained from MENDOCINO. (Calif. Stats. 1852, 3d sess., ch. 116/p. 192)

SIERRA created from YUBA. (Calif. Stats. 1852, 3d sess., ch. 145/pp. 230–231)

20 April 1852

TULARE created from MARIPOSA. (Calif. Stats. 1852, 3d sess., ch. 153/pp. 240–242)

24 April 1852

SANTA BARBARA gained from SAN LUIS OBISPO. (Calif. Stats. 1852, 3d sess., ch. 133/p. 218)

SHASTA boundaries redefined [no change]. (Calif. Stats. 1852, 3d sess., ch. 142/p. 228)

3 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)

BUTTE exchanged with SUTTER. (Calif. Stats. 1852, 3d sess., ch. 149/p. 237)

NEVADA gained from SIERRA. (Calif. Stats. 1852, 3d sess., chs. 114–115/pp. 190–192)

SONOMA lost Mare Island when SONOMA boundaries were redefined. Mare Island remained a non-county area until 27 January 1853. (Calif. Stats. 1852, 3d sess., ch. 147/p. 236)

27 January 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)

19 March 1853

BUTTE boundaries clarified [no change]. (Calif. Stats. 1853, 4th sess., ch. 37/p. 53)

25 March 1853

ALAMEDA created from CONTRA COSTA and SANTA CLARA; SANTA CLARA gained small remnant from CONTRA COSTA. (Calif. Stats. 1853, 4th sess., ch. 41/pp. 56–59)

26 April 1853

SAN BERNARDINO created from LOS ANGELES. (Calif. Stats. 1853, 4th sess., ch. 78/pp. 119–123)

12 May 1853

HUMBOLDT created from TRINITY. (Calif. Stats. 1853, 4th sess., ch. 114/pp. 161–164)

31 March 1854

SUTTER gained from BUTTE. (Calif. Stats. 1854, 5th sess., ch. 16/p. 26)

1 April 1854

PLUMAS created from BUTTE. (Calif. Stats. 1854, 5th sess., ch. 1/pp. 129–131)

5 April 1854

STANISLAUS created from TUOLUMNE. (Calif. Stats. 1854, 5th sess., chs. 35, 81/pp. 40–41, 191–194)

13 May 1854

SAN LUIS OBISPO exchanged with SANTA BARBARA. (Calif. Stats. 1854, 5th sess., ch. 24/p. 148)

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)

14 June 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)

4 April 1855

NAPA gained from MENDOCINO, SOLANO, and SONOMA. (Calif. Stats. 1855, 6th sess., ch. 68/p. 77)

16 April 1855

AMADOR gained from EL DORADO. (Calif. Stats. 1855, 6th sess., ch. 92/p. 113)

19 April 1855

MERCED created from MARIPOSA. (Calif. Stats. 1855, 6th sess., ch. 104/pp. 125–128)

23 April 1855

AMADOR boundaries redefined [no change]. (Calif. Stats. 1855, 6th sess., ch. 113/p. 134–135)

27 April 1855

SONOMA gained from MARIN, exchanged with MENDOCINO, lost to SOLANO. (Calif. Stats. 1855, 6th sess., ch. 125/p. 150)

30 April 1855

TRINITY gained from KLAMATH (extinct). (Calif. Stats. 1855, 6th sess., ch. 156/p. 200)

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)

4 May 1855

Boundary between STANISLAUS and TUOLUMNE clarified [no change]. (Calif. Stats. 1855, 6th sess., ch. 194/p. 245)

26 March 1856

LOS ANGELES boundaries redefined [no change]. (Calif. Stats. 1856, 7th sess., ch. 46/p. 53)

9 April 1856

TEHAMA created from BUTTE, COLUSI (now COLUSA), and SHASTA. (Calif. Stats. 1856, 7th sess., ch. 100/pp. 118–119)

16 April 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)

19 April 1856

COLUSI (now COLUSA) gained from BUTTE, SUTTER, and YOLO. (Calif. Stats. 1856, 7th sess., ch. 105/p. 124)

FREZNO (now FRESNO) created from CALAVERAS, MARIPOSA, MERCED, TULARE, and TUOLUMNE; TULARE gained from MERCED. (Calif. Stats. 1856, 7th sess., ch. 127/p. 183)

NEVADA gained from SIERRA. (Calif. Stats. 1856, 7th sess., ch. 122/p. 143)

21 April 1856

SHASTA exchanged with TEHAMA. (Calif. Stats. 1856, 7th sess., ch. 141/p. 222)

SUTTER gained from BUTTE. (Calif. Stats. 1856, 7th sess., ch. 150/p. 231)

1 July 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)

19 February 1857

TEHAMA exchanged with SHASTA, lost to COLUSI (now COLUSA). (Calif. Stats. 1857, 8th sess., ch. 37/p. 25)

2 March 1857

DEL NORTE created from KLAMATH (extinct) and a small area of SISKIYOU. (Calif. Stats. 1857, 8th sess., ch. 52/pp. 35–36)

26 March 1857

TEHAMA boundaries redefined [no change]. (Calif. Stats. 1857, 8th sess., ch. 105/p. 109)

YOLO gained from SOLANO. (Calif. Stats. 1857, 8th sess., ch. 104/p. 108)

30 March 1857

SACRAMENTO boundaries redefined [no change]. (Calif. Stats. 1857, 8th sess., ch. 120/p. 132)

2 April 1857

SAN BERNARDINO boundaries redefined [no change]. (Calif. Stats. 1857, 8th sess., ch. 142/p. 165)

18 April 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., ch. 192/pp. 222–223; Stanger, 88)

SAN FRANCISCO gained Angel Island in San Francisco Bay from MARIN. (Calif. Stats. 1857, 8th sess., ch. 190/pp. 209–210)

25 April 1857

AMADOR exchanged with EL DORADO. (Calif. Stats. 1857, 8th sess., ch. 220/p. 251)

11 February 1858

DEL NORTE boundaries clarified [no change]. (Calif. Stats. 1858, 9th sess., ch. 23/p. 21)

by January 1859

Spelling of ";COLUSI"; changed to ";COLUSA."; (Calif. Stats. 1859, 10th sess.; [Green], 44–45)

11 March 1859

MENDOCINO gained from HUMBOLDT and TRINITY, exchanged with SONOMA. (Calif. Stats. 1859, 10th sess., ch. 108/pp. 98–99)

8 April 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)

11 April 1859

TUOLUMNE gained from FREZNO (now FRESNO). (Calif. Stats. 1859, 10th sess., ch. 204/p. 213)

19 April 1859

TEHAMA gained from COLUSA, lost to BUTTE. (Calif. Stats. 1859, 10th sess., ch. 322/p. 359)

2 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)

17 February 1860

STANISLAUS gained from SAN JOAQUIN. (Calif. Stats. 1860, 11th sess., ch. 62/pp. 34–35)

22 March 1860

YUBA gained small area in village of Strawberry Valley from BUTTE [change too small to display on interactive map; shapefile users see small_changes 1860_pt. for location]. (Calif. Stats. 1860, 11th sess., ch. 145/p. 115)

25 April 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)

28 April 1860

HUMBOLDT and TRINITY gained from MENDOCINO. (Calif. Stats. 1860, 11th sess., ch. 340/p. 334)

15 April 1861

YUBA gained small area at Woodville from BUTTE [change too small to display on interactive map; shapefile users see small_changes 1861_pt. for location]. (Calif. Stats. 1861, 12th sess., ch. 166/p. 167)

23 April 1861

SACRAMENTO gained from SAN JOAQUIN. (Calif. Stats. 1861, 12th sess., ch. 219/p. 221; Tinkham, 64–65)

24 April 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)

13 May 1861

SAN LUIS OBISPO gained from MONTEREY. (Calif. Stats. 1861, 12th sess., ch. 342/p. 349)

SONOMA gained from MARIN [repealed part of act of 25 April 1860]. (Calif. Stats. 1861, 12th sess., ch. 346/p. 351)

20 May 1861

LAKE created from NAPA. (Calif. Stats. 1861, 12th sess., ch. 498/pp. 560–561)

11 February 1862

HUMBOLDT boundaries redefined [no change]. (Calif Laws 1862, 13th sess., ch. 11/p. 6)

by April 1862

Phonetic spelling of ";FREZNO"; changed to ";FRESNO."; (Calif. Stats. 1863, 13th sess.; Gudde, 138)

27 March 1863

SIERRA gained from PLUMAS. (Calif. Stats. 1863, 14th sess., ch. 101/p. 114; Sinnott, 6:19–22)

8 April 1863

AMADOR gained from EL DORADO. (Calif. Stats. 1863, 14th sess., ch. 170/p. 231)

20 April 1863

EL DORADO gained from PLACER. (Calif. Stats. 1863, 14th sess., ch. 263/p. 349)

MONTEREY gained from SAN LUIS OBISPO. (Calif. Stats. 1863, 14th sess., ch. 276/p. 358)

29 February 1864

LAKE gained from MENDOCINO and NAPA. (Calif. Stats. 1863–1864, 15th sess., ch. 122/p. 111)

16 March 1864

ALPINE created from AMADOR, CALAVERAS, EL DORADO, MONO, and TUOLUMNE. (Calif. Stats. 1863–1864, 15th sess., ch. 180/pp. 178–182)

1 April 1864

LASSEN created from PLUMAS and SHASTA. (Calif. Stats. 1863–1864, 15th sess., ch. 261/pp. 264–269)

SUTTER gained from BUTTE. (Calif. Stats. 1863–1864, 15th sess., ch. 292/p. 301)

4 April 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)

2 March 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)

3 March 1866

YOLO boundaries clarified [no change]. (Calif. Stats. 1865, 16th sess., ch. 181/p. 162; ";Waters v. Pool,"; in Calif. Rpts., 130:136–139)

8 March 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 March 1866

PLACER exchanged with SUTTER; SACRAMENTO boundaries redefined [no change]. (Calif. Stats. 1865, 16th sess., ch. 224/p. 223)

SIERRA gained from YUBA. (Calif. Stats. 1865, 16th sess., ch. 229/p. 228)

22 March 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)

26 March 1866

LASSEN boundaries clarified [no change]. (Calif. Stats. 1865, 16th sess., ch. 371/p. 453)

31 March 1866

PLUMAS gained from SIERRA and gained small area from YUBA. (Calif. Stats. 1865, 16th sess., ch. 466/p. 605)

2 April 1866

KERN created from LOS ANGELES and TULARE. (Calif. Stats. 1865, 16th sess., ch. 569/pp. 796–798)

10 February 1868

KERN gained from TULARE. (Calif. Stats. 1867, 17th sess., ch. 43/p. 40)

SONOMA boundaries redefined [no change]. (Calif. Stats. 1867, 17th sess., ch. 45/p. 42)

13 February 1868

Boundary between MERCED and STANISLAUS redefined to confirm 1854 STANISLAUS line [no change; see 8 March 1866]. (Calif. Stats. 1867, 17th sess., ch. 57/p. 56)

16 March 1868

SAN MATEO gained from SANTA CRUZ. (Calif. Stats. 1867, 17th sess., ch. 195/p. 174)

24 March 1868

LAKE gained from COLUSA, NAPA, and YOLO. (Calif. Stats. 1867, 17th sess., ch. 257/p. 269)

26 March 1868

CONTRA COSTA gained the Brothers Islands from MARIN. (Calif. Stats. 1867, 17th sess., ch. 305/p. 347)

28 March 1868

SIERRA gained small area from PLUMAS. (Calif. Stats. 1867, 17th sess., ch. 377/p. 462)

30 March 1868

SAN DIEGO boundaries clarified [no change]. (Calif. Stats. 1867, 17th sess., ch. 453/p. 604)

22 January 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)

12 March 1870

SACRAMENTO gained small areas from SOLANO and YOLO. (Calif. Stats. 1869, 18th sess., ch. 191/p. 294)

28 March 1870

INYO gained from MONO. (Calif. Stats. 1869, 18th sess., ch. 323/p. 421)

29 March 1870

MARIPOSA gained from FRESNO. (Calif. Stats. 1869, 18th sess., ch. 341/p. 449)

8 March 1872

NAPA gained from LAKE. (Calif. Stats. 1871, 19th sess., ch. 229/p. 305)

1 April 1872

FRESNO gained from MARIPOSA. (Calif. Stats. 1871, 19th sess., ch. 602/p. 891)

30 October 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)

1 January 1873

COLUSA gained from TEHAMA, lost to BUTTE. (Political Code 1872, 1: secs. 3915–3916, 3922/pp. 118–119, 123–124)

DEL NORTE exchanged with SISKIYOU. (Political Code 1872, 1: secs. 3909, 3913/pp. 113–114, 117)

INYO gained from KERN and SAN BERNARDINO. (Political Code 1872, 1: secs. 3941–3943/pp. 139–140)

Boundary of KERN with VENTURA adjusted to run partially on public land survey lines. (Political Code 1872, 1: secs. 3940–3942/pp. 138–139)

LASSEN and SHASTA gained from PLUMAS. (Political Code 1872, 1: secs. 3911–3912, 3920/pp. 115–116, 122–123)

PLACER gained small area from SUTTER. (Political Code 1872, 1: sec. 3924, 3926/pp. 125–127)

SAN DIEGO gained from LOS ANGELES, lost to SAN BERNARDINO. (Political Code 1872, 1: secs. 3943–3945/pp. 140–142)

SAN LUIS OBISPO exchanged with SANTA BARBARA. (Political Code 1872, 1: secs. 3946–3947/pp. 142–143)

TULARE gained from KERN. (Political Code 1872, 1: secs. 3940–3941/pp. 138–139)

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)

11 February 1874

Boundary between FRESNO and MARIPOSA redefined [no change]. (Calif. Stats. 1873, 20th sess., ch. 88/p. 100)

12 February 1874

SAN BENITO created from MONTEREY. (Calif. Stats. 1873, 20th sess., ch. 87/pp. 95–99)

17 February 1874

MODOC created from SISKIYOU. (Calif. Stats. 1873, 20th sess., ch. 107/pp. 124–129)

7 March 1874

BUTTE boundaries clarified [no change]. (Calif. Stats. 1873, 20th sess., Acts Amendatory of the Codes, p. 167)

16 March 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)

27 March 1874

FRESNO exchanged with TULARE. (Calif. Stats. 1873, 20th sess., ch. 468/p. 700)

30 March 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 [change too small to display on interactive map; shapefile users see small_changes 1874_pt. for location]. (Calif. Stats. 1873, 20th sess., Acts Amendatory of the Codes, pp. 168–170; Coy, 62–63)

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)

23 March 1876

FRESNO exchanged with TULARE. (Calif. Stats. 1875, 21st sess., ch. 301/p. 397)

5 February 1877

SAN BERNARDINO gained from LOS ANGELES as a result of an official survey of the boundary. (Coy, 149, 217–219)

14 March 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)

1 April 1878

SAN JOAQUIN gained from SACRAMENTO. (Calif. Stats. 1877, 22d sess., Acts Amendatory of the Political Code, ch. 636/p. 70)

July 1881

VENTURA gained from LOS ANGELES as a result of an official boundary survey. (Coy, 150–154, 292)

14 March 1885

KERN exchanged with SAN LUIS OBISPO. (Calif. Stats. 1885, 26th sess., ch. 149/pp. 139–141)

11 March 1887

DEL NORTE exchanged with SISKIYOU. (Calif. Stats. 1887, 27th sess., ch. 88/pp. 105–107)

SAN BENITO gained from FRESNO and gained a small area from MERCED. (Calif. Stats. 1887, 27th sess., ch. 86/p.103)

19 March 1889

PLACER boundaries clarified [no change]. (Calif. Stats. 1889, 28th sess., ch. 262/p. 402)

4 June 1889

ORANGE created from LOS ANGELES. Act passed 11 March 1889; referendum for or against creation of the new county held 4 June 1889. (Calif. Stats. 1889, 28th sess., ch. 110/pp. 123–129)

31 March 1891

SUTTER gained small area from COLUSA [change too small to display on interactive map; shapefile users see small_changes 1891_pt. for location]. (Calif. Stats. 1891, 29th sess., ch. 240/p. 455)

5 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 March 1893

COLUSA gained from GLENN. (Calif. Stats. 1893, 30th sess., ch. 141/p. 158)

2 May 1893

RIVERSIDE created from SAN BERNARDINO and SAN DIEGO. Act passed 11 March 1893; referendum for or against creation of the new county held 2 May 1893. (Calif. Stats. 1893, 30th sess., ch. 142/pp. 158–168)

16 May 1893

MADERA created from FRESNO. Act passed 11 March 1893; referendum for or against creation of the 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)

23 May 1893

KINGS created from TULARE. Act passed 22 March 1893; referendum for or against creation of the 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)

25 February 1897

BUTTE exchanged with YUBA. (Calif. Stats. 1897, 32d sess., ch. 26/p. 22)

14 March 1899

LASSEN gained from SHASTA. (Calif. Stats. 1899, 33d sess., ch. 82/p. 98)

28 February 1901

LASSEN exchanged with PLUMAS. (Calif. Stats. 1901, 34th sess., ch. 61/pp. 76–80)

14 March 1901

SAN MATEO boundaries clarified [no change]. (Calif. Stats. 1901, 34th sess., ch. 128/p. 291)

23 March 1901

BUTTE exchanged with PLUMAS. (Calif. Stats. 1901, 34th sess., ch. 146/pp. 549–551)

HUMBOLDT exchanged with DEL NORTE, lost small area to SISKIYOU. (Calif. Stats. 1901, 34th sess., ch. 193/p. 600)

Boundary between PLUMAS and SHASTA clarified to run on public land survey line [no discernible change]. (Calif. Stats. 1901, 34th sess., ch. 171/p. 560)

18 March 1905

Boundary between SACRAMENTO and SAN JOAQUIN redefined [no change]. (Calif. Stats. 1905, 36th sess., ch. 167/p. 164)

8 March 1907

MENDOCINO gained from LAKE, lost to GLENN. (Calif. Stats. 1907, 37th sess., ch. 113/p. 135)

14 March 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,"; inCalif. Rpts., 152:224–241)

12 August 1907

IMPERIAL created from SAN DIEGO. (Coy, 50–51; Farr, 18–19)

28 December 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)

1 March 1909

SIERRA boundaries clarified; NEVADA boundary with SIERRA clarified to run on public land survey lines [no discernible change]. (Calif. Stats. 1909, 38th sess., ch. 75/p. 86)

13 March 1909

GLENN exchanged with LAKE; boundary of LAKE with COLUSA and MENDOCINO redefined [no change]. (Calif. Stats. 1909, 38th sess., ch. 211/pp. 326–328)

12 April 1909

KINGS gained from FRESNO. (Calif. Stats. 1909, 38th sess., ch. 483/pp. 827–829)

10 August 1913

EL DORADO exchanged with PLACER. (Calif. Stats. 1913, 40th sess., chs. 315–316/pp. 603–605)

8 August 1915

BUTTE gained small area in section 3, township 19 north, range 1 east from GLENN [change too small to display on interactive map; shapefile users see small_changes 1915_pt. for location]. (Calif. Stats. 1915, 41st sess., ch. 532/p. 898)

27 July 1917

SAN BERNARDINO gained from KERN. (Calif. Stats. 1917, 42d sess., ch. 205/p. 301)

30 July 1917

MENDOCINO exchanged with SONOMA. (Calif. Stats. 1917, 42d sess., ch. 725/p. 1396)

31 July 1917

LAKE exchanged with MENDOCINO. (Calif. Stats. 1917, 42d sess., ch. 779/pp. 1635–1640)

22 July 1919

RIVERSIDE exchanged with SAN BERNARDINO. (Calif. Stats. 1919, 43d sess., ch. 62/p. 99)

23 July 1919

The new Political Code authorized LOS ANGELES to exchange with VENTURA. This chapter of the 1919 revision of state 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)

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. The change was confirmed in 1923 by the 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 and VENTURA boundaries redefined; see 23 July 1919 [no change]. (Calif. Laws 1923, 45th sess., ch. 160, secs. 16, 57/pp. 336, 373)

20 November 1944

BUTTE exchanged with TEHAMA. (Coy, 339, 345)

19 September 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)

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";)

9 September 1953

SUTTER exchanged with YUBA along Bear River. (Calif. Stats. 1953, reg. sess., ch. 836/pp. 2148–2156)

11 September 1957

SAN BERNARDINO gained small area from INYO; boundaries of INYO and SAN BERNARDINO clarified, ending boundary dispute dating from 1947. (Calif. Stats. 1957, reg. sess., ch. 2382/p. 4119)

14 January 1958

ALAMEDA gained small area from CONTRA COSTA [change too small to display on interactive map; shapefile users see small_changes 1958_pt. for location]. (Coy, 338–339)

13 May 1963

KERN exchanged small areas with SAN BERNARDINO. (Coy, 340, 342; correspondence, California Board of Equalization, 25 July 2002)

14 October 1963

SANTA CLARA gained small area from SAN MATEO [change too small to display on interactive map; shapefile users see small_changes 1963_pt. for location]. (Coy, 342–343, 345)

16 June 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)

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)

11 July 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)

5 June 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)

11 July 1968

SAN MATEO and SANTA CLARA boundaries clarified [no change]. (Calif. Stats. 1968, reg. sess., ch. 537/pp. 1189–1193)

2 November 1971

SANTA CLARA gained small areas from ALAMEDA [change too small to display on interactive map; shapefile users see small_changes 1971_pt. for location]. (Coy, 338, 343)

17 November 1971

SANTA CLARA exchanged small areas with SANTA CRUZ as the boundary was clarified along its entire length [not mapped]. (Coy, 343–345)

1972

Boundary between INYO and SAN BERNARDINO adjusted [precise location unknown, not mapped]. (Correspondence, California State Board of Equalization, 25 July 2002)

7 April 1976

SANTA CLARA and SANTA CRUZ boundaries clarified [no change]. (Calif. Stats. 1976, reg. sess., ch. 102/pp. 161–165)

1 January 1980

YOLO gained small area from SOLANO. Ordinance passed 20 November 1979; effective 1 January 1980 [change too small to display on interactive map; shapefile users see small_changes 1980_pt. for location]. (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)

1 June 1982

Boundary between California and Nevada in Lake Tahoe was clarified by the United States Supreme Court [no change]. (“California v. Nevada,” in U.S. Rpts., 456:867–869; “California v. Nevada,” in U.S. Rpts., 447:125–133)

2 July 1986

STANISLAUS boundaries clarified [no change]. (Calif. Stats. 1985–1986, reg. sess., ch. 248, sec. 80/p. 1239)

31 December 1986

FRESNO gained small area from TULARE. Ordinance passed 18 November 1986; effective 31 December 1986 [change too small to display on interactive map; shapefile users see small_changes 1986_pt. for location]. (Minutes of the Board of Supervisors, Tulare County, 18 November 1986, ordinance 2745)

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)

1 September 1987

ORANGE gained small area in Cypress Memorial Park Cemetery from LOS ANGELES. Ordinance passed 29 July 1987; effective 1 September 1987 [change too small to display on interactive map; shapefile users see small_changes 1987_pt. for location]. (Minutes of the Board of Supervisors, Orange County, 29 July 1987, ordinance 3647)

14 July 1988

SACRAMENTO boundaries redefined [no change]. (Calif. Stats. 1987–1988, reg. sess., ch. 363/p. 1676)

8 November 1988

ORANGE exchanged small areas with RIVERSIDE. Ordinance passed 27 September 1988; took effect 8 November 1988. (Minutes of the Board of Supervisors, Riverside County, 27 September 1988, ordinance 665)

2 May 1991

SANTA BARBARA gained small area from SAN LUIS OBISPO [change too small to display on interactive map; shapefile users see small_changes 1991_pt. for location]. (Leaha K. Magee, San Luis Obispo County LAFCO, correspondence, 29 October 2002)

10 June 1991

KERN gained from VENTURA. (Calif. Stats. 1991–1992, reg. sess., ch. 51/p. 150)

30 June 1991

AMADOR gained small area from EL DORADO. Ordinance passed 25 June 1991; effective 30 June 1991 [change too small to display on interactive map; shapefile users see small_changes 1991_pt. for location]. (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)

30 September 1991

FRESNO exchanged small areas with TULARE. Ordinance passed 3 September 1991; effective 30 September 1991 [change too small to display on interactive map; shapefile users see small_changes 1991_pt. for location]. (Minutes of the Board of Supervisors, Tulare County, 3 September 1991, ordinance 2970)

1 March 1992

SAN BERNARDINO gained small area from LOS ANGELES. Ordinance passed 27 January 1992; effective 1 March 1992 [change too small to display on interactive map; shapefile users see small_changes 1992_pt. for location]. (Minutes of the Board of Supervisors, San Bernardino County, 27 January 1992, ordinance 3478)

1 July 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)

9 July 1992

SANTA BARBARA gained small area from SAN LUIS OBISPO [change too small to display on interactive map; shapefile users see small_changes 1992_pt. for location]. (Leaha K. Magee, San Luis Obispo County LAFCO, correspondence, 29 October 2002)

1 September 1992

ALAMEDA gained small area from CONTRA COSTA. Ordinance passed 11 August 1992; effective 1 September 1992 [change too small to display on interactive map; shapefile users see small_changes 1992_pt. for location]. (Minutes of the Board of Supervisors, Alameda County, 11 August 1992, ordinance 92-57)

18 December 1992

YOLO gained small area from SOLANO [change too small to display on interactive map; shapefile users see small_changes 1992_pt. for location]. (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)

11 October 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)

ORANGE and RIVERSIDE boundaries redefined [no change]. (Calif. Stats. 1993–1994, reg. sess., ch. 1195, secs. 4–5/pp. 6855–6860)

SAN BERNARDINO gained small area from LOS ANGELES [change too small to display on interactive map; shapefile users see small_changes 1993_pt. for location]. (Calif. Stats. 1993–1994, reg. sess., ch. 1195, sec. 3/p. 6854)

28 March 1994

YUBA gained small area from SUTTER [change too small to display on interactive map; shapefile users see small_changes 1994_pt. for location]. (Minutes of the Board of Supervisors, Yuba County, 20 July 1993, ordinance 1140)

4 October 1995

CONTRA COSTA gained small area from ALAMEDA [change too small to display on interactive map; shapefile users see small_changes 1995_pt. for location]. (Calif. Stats. 1995, reg. sess., ch. 529, sec. 3 in Official California Legislative Information, http://www.leginfo.ca.gov/statute.html, 23 September 2002)

17 November 1995

ALPINE gained small area from AMADOR. Ordinance passed 3 October 1995; effective 17 November 1995 [change too small to display on interactive map; shapefile users see small_changes 1995_pt. for location]. (Minutes of the Board of Supervisors, Amador County, 3 October 1995, ordinance 1390)

19 August 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)

11 December 1998

SANTA CLARA gained small area from SANTA CRUZ [precise location unknown, not mapped]. (Correspondence, California State Board of Equalization, 25 July 2002)

30 September 1999

ORANGE gained small area from LOS ANGELES [change too small to display on interactive map; shapefile users see small_changes 1999_pt. for location]. (Minutes of the Board of Supervisors, Los Angeles County, 24 August 1999, ordinance 99-0077M)

19 September 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)