CSGA LogoCalifornia Counties
Content Last Verified: 2 Jun 2014

County Name Established Date Parent County County Seat
Alameda28 Mar 1853Contra Costa, Santa ClaraOakland
Alpine16 Mar 1864Amador, Calaveras, El Dorado, Mono, TuolumneMarkleeville
Amador 11 May 1854Calaveras,(El Dorado 1855, 1857, 1863)Jackson
Branciforte18 Feb 1850Original County, renamed (see) Santa Cruz 5 Apr 1850
Butte18 Feb 1850Original CountyOroville
Calaveras18 Feb 1850Original CountySan Andreas
Colusa18 Feb 1850Original County, Pre 1855 aka Colusi and Coluse (Butte 1851, 1856; Sutter Contra Costa,18 Feb 1850,Original CountyMartinez
Contra Costa18 Feb 1850Original CountyMartinez
Coso1864Renamed (see) Inyo 1866
Del Norte2 Mar 1857Klamath (Humboldt 1901; Siskiyou 1887)Crescent City
El Dorado18 Feb 1850Original CountyPlacerville
FremontProposed, renamed Yola, became (see) Yolo
Fresno19 Apr 1856Mariposa, Merced (Tulare1856, 1876)Fresno
Glenn11 Mar 1891Colusa (Mendocino 1907) Willows
Humboldt12 May 1853Trinity (Del Norte 1901; Klamath 1875 Mendocino 1860)Eureka
Imperial6-Aug-07San Diego Note: Last county to be organized.El Centro
Inyo22 Mar 1866Tulare (Kern 1872; Mono 1866, 1870; San Bernardino 1872)Independence
Kern2 Apr 1866Tulare, Los Angeles, San Luis ObispoBakersfield
Kings22 Mar 1893Tulare (Fresno 1909) Hanford
Klamath25 Apr 1851Trinity, Abolished 22 Apr 1874
Lake20 May 1861Napa (Colusa 1868; Mendocino 1874)Lakeport
Lassen1 Apr 1864Shasta (Plumas 1864, 1872)Susanville
Los Angeles18 Feb 1850Original CountyLos Angeles
Madera11 Mar 1893Fresno Madera
Marin18 Feb 1850Original County, San Rafael
Mariposa18 Feb 1850Original County,(Fresno 1870)Mariposa
Mendocino18 Feb 1850Original County (Sonoma 1855, 1859)Ukiah
Merced19 Apr 1855MariposaMerced
Modoc17 Feb 1874SiskiyouAlturas
Mono24 Apr 1861Calaveras, Fresno (Amador [unattached] 1866)Bridgeport
Monterey18 Feb 1850Original County (San Luis Obispo 1851, 1863, 1872)Salinas
Mount Diablo CountyProposed, renamed (see) Contra Costa County
Napa18 Feb 1850Original County (Lake 1972; Solano 1855; Sonoma 1855)Napa
Nevada25 Apr 1851Yuba (Sierra 1856; Yuba 1852)Nevada City
Orange11 Mar 1889Los AngelesSanta Ana
OroProposed, renamed (see) Tuolumne
Placer25 Apr 1851Sutter, Yuba (El Dorado 1913)Auburn
Plumas18 Mar 1854Butte (Sierra 1866) Quincy
Putah1852Was to include land in Nevada, US never ceded, repealed in 1859
ReddingProposed, renamed (see) Shasta,,
Riverside11 Mar 1893San Bernardino, San DiegoRiverside
Sacramento18 Feb 1850Original CountySacramento
San Benito12 Feb 1874Monterey (Fresno 1887; Merced 1887)Hollister
San Bernardino26 Apr 1853Los Angeles 1853, 1878San Bernardino
San Diego18 Feb 1850Original CountySan Diego
San Francisco18 Feb 1850Original CountySan Francisco
San Joaquin18 Feb 1850Original County (Sacramento 1878)Stockton
San Luis Obispo18 Feb 1850Original County (Kern 1885; Monterey 1861; Santa Barbara 1854, 1872)San Luis Obispo
San Mateo19 Apr 1856San Francisco (Santa Cruz 1868)Redwood City
Santa Barbara18 Feb 1850Original County (San Luis Obispo 1852, 1872) Santa Barbara
Santa Clara18 Feb 1850Original CountySan Jose
Santa Cruz18 Feb 1850Original CountySanta Cruz
Shasta18 Feb 1850Original County (Plumas 1872)Redding
Sierra16 April 1852Yuba (Plumas 1863, 1868; Yuba, 1866)Downieville
Siskiyou22 Mar 1852Shasta, Klamath, (Del Norte 1887; Klamath 1875)Yreka
Solano18 Feb 1850Original County (Sonoma 1853)Fairfield
Sonoma18 Feb 1850Original CountySanta Rosa
Stanislaus1 Apr 1854Tuolumne (Merced 1868; San Joaquin 1860)Modesto
Sutter18 Feb 1850Original County (Placer 1866; Butte 1852, 1854, 1866)Yuba City
Tehama9 Apr 1856Colusa (Butte 1856,1857; Shasta 1856,1857) Red Bluff
Trinity18 Feb 1850Original County (Klamath 1855; Mendocino 1860, 1872)Weaverville
Tulare20 Apr 1852Mariposa (Fresno 1874)Visalia
Tuolumne18 Feb 1850Original CountySonora
Ventura22 Mar 1872Santa Barbara, San Luis Obispo (Los Angeles 1881)Ventura
Yolo18 Feb 1850Original County (Solano 1857)Woodland
Yuba18 Feb 1850Original CountyMarysville

" The Birth of Each County and Later Significant Boundary Changes - County Listings." California Counties. Sacramento: California State Association of Counties, 2009.
"California." Redbook: American state, county and town sources. Alice Eichholz, ed. Provo: Ancestry, 2004. Pages 81-83.
"California." The Handybook for Genealogists. Logan: Everton Publishers, 2006. Pages 75-82.
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