California County Creation Dates and Parent Counties
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See an interactive outline map of California Historical Counties at Newberry Library site[1] (Free) Enter a year, Refresh Map, select zoom in, then click on the map to enlarge it. |
| Tip: Sort the table by Date Formed or by Parent Counties and check Boundary Changes for interesting insights. |
| Name of County | Date Formed | Boundary Changes |
Parent County | Counties Created by Boundary Changes |
| Alameda | 1853 Mar 25 | Details | Contra Costa, Santa Clara | none |
| Alpine | 1864 Mar 16 | Details | Eldorado, Calaveras, Amador | none |
| Amador | 1854 May 1 | Details | Calaveras | Alpine 1864 |
| Branciforte | 1850 Feb 18 | Details | California Lands | renamed Santa Cruz |
| Butte | 1850 Feb 18 | Details | Calfornia Lands | Plumas 1854, Tehama 1856 |
| Calaveras | 1850 June 18 | Details | California Lands | Alpine 1864, Amador 1854, Mono 1861 |
| Colusa | 1850 Feb 18 | Details | California Lands | Glenn 1891, Tehama 1856 |
| Contra Costa | 1850 Feb 18 | Details | California Lands | Alameda 1853 |
| Del Norte | 1857 July 2 | Details | Humboldt | none |
| El Dorado | 1850 Feb 18 | Details | California Lands | Alpine 1864 |
| Fresno | 1856 Apr 19 | Details | Marced, Mariposa | Kings 1893, Madra 1893, Mono 1861 |
| Glenn | 1891 May 5 | Details | Colusa | none |
| Humboldt | 1853 May 12 | Details | California Lands | Del Norte 1857 |
| Imperial | 1907 Aug 6 | Details | San Diego | none |
| Inyo | 1866 Mar 22 | Details | Tulare | none |
| Kern | 1866 September 2 | Details | Tulare, Los Angeles | none |
| Kings | 1893 Mar 22 | Details | Fresno, Tulare | none |
| Klamath | 1850 Feb 18 | Details | California Lands | renamed Siskiyou 1852 |
| Lake | October 20 |
Details | Tuolumne | none |
| Lassen | 1864 pr 1 | Details | Plumas, Shasta | none |
| Los Angeles | 1850 Feb 18 | Details | California Lands | Kern 1866, Orange 1889, San Bernardino 1853 |
| Madera | 1893 November 11 | Details | Fresno | none |
| Marin | 1850 Feb 18 | Details | California Lands | none |
| Mariposa | 1850 Feb 18 | Details | California Lands | Fresno 1856, Merced 1855, Tulare 1852 |
| Mendocino | 850 December 18 | Details | California Lands | none |
| Merced | 1855 Apr 19 | Details | Mariposa | Fresno 1856 |
| Modoc | 874 Feb 17 | Details | Siskiyou | none |
| Mono | 1861 January 24 | Details | Calaveras, Fresno | none |
| Monterey | 1850 Feb 18 | Details | California Lands | San Benito 1874 |
| Napa | 1850 Feb 18 | Details | California Lands | none |
| Nevada | 1851 February 25 | Details | Yuba | none |
| Orange | 1889 Mar 11 | Details | Los Angeles | none |
| Placer | 1851 Apr 25 | Details | Yuba, Sutter | none |
| Plumas | 1854 March 18 | Details | Butte | Lassen 1864 |
| Riverside | 1893 Mar 11 | Details | San Diego, San Bernardino | none |
| Sacramento | 1850 Feb 18 | Details | California Lands | none |
| San Benito | 1874 April 12 | Details | Monterey | none |
| San Bernardino | 1853 Apr 26 | Details | Los Angeles | Riverside 1893 |
| San Diego | 1850 Feb 18 | Details | California Lands | Imperial 1907, Riverside 1893 |
| San Francisco | 1850 May 18 | Details | California Lands | San Mateo 1856 |
| San Joaquin | 1850 Feb 18 | Details | California Lands | none |
| San Luis Obispo | 1850 Feb 18 | Details | California Lands | none |
| San Mateo | 1856 June 18 | Details | San Francisco | none |
| Santa Barbara | 1850 Feb 18 | Details | California Lands | none |
| Santa Clara | 1850 Feb 18 | Details | California Lands | none |
| Santa Cruz | 1850 July 19 | Details | renamed from Branciforte | none |
| Shasta | 1850 Feb 18 | Details | California Lands | Lassen 1864, Siskiyou 1852, Tehama 1856 |
| Sierra | 1852 Feb 16 | Details | Yuba | none |
| Siskiyou | 1852 August 22 | Details | renamed from Klamath | none |
| Solano | 1850 Feb 18 | Details | California Lands | none |
| Sonoma | 850 Feb 18 | Details | California Lands | none |
| Stanislaus | 1854 September 1 | Details | Tuolumne | none |
| Sutter | 1850 Feb 18 | Details | California Lands | Placer 1851 |
| Tehama | 1856 pr 9 | Details | Colusa, Butte, Shasta | none |
| Trinity | 1850 October 18 | Details | California Lands | none |
| Tulare | 1852 Apr 20 | Details | Mariposa | Inyo 1866, Kern 1866, Kings 1893 |
| Tuolumne | 1850 Feb 18 | Details | California Lands | Lake 1861, Stanislaus 1854 |
| Ventura | 1872 November 22 | Details | Santa Barbara | none |
| Yolo | 1850 Feb 18 | Details | California Lands | none |
| Yuba | 1850 Feb 18 | Details | California Lands | Nevada 1851, Placer 1851, Sierra 1852
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- ↑ [http://historical-county.newberry.org/website/California/viewer.htm California Atlas of Historical County Boundaries, John H. Long, Editor; Peggy Tuck Sinko, Associate Editor; Gordon DenBoer, Historical Compiler; Douglas Knox, Book Digitizing Director and Digital Compiler; Emily Kelley, Research Associate; Laura Rico-Beck, GIS Specialist; Peter Siczewicz, ArcIMS Interactive Map Designer; Robert Will, Cartographic Assistant. Copyright The Newberry Library 2008.