Alameda County (1853 - Present)
Alpine County (1864 - Present)
Amador County (1854 - Present)
Branciforte County (1850 - Present)
Buena Vista County Proposed (1855 - 1856)
Butte County (1850 - Present)
Calaveras County (1850 - Present)
Colusi County (1850 - Present)
Contra Costa County (1850 - Present)
Coso County Proposed (1864 - 1864)
Del Norte County (1857 - Present)
El Dorado County (1850 - Present)
Frezno County (1856 - Present)
Glenn County (1891 - Present)
Humboldt County (1853 - Present)
Imperial County (1907 - Present)
Inyo County (1866 - Present)
Kern County (1866 - Present)
Kings County (1893 - Present)
Klamath County (1851 - 1874)
Lake County (1861 - Present)
Lassen County (1864 - Present)
Los Angeles County (1850 - Present)
Madera County (1893 - Present)
Marin County (1850 - Present)
Mariposa County (1850 - Present)
Mendocino County (1850 - Present)
Merced County (1855 - Present)
Modoc County (1874 - Present)
Mono County (1861 - Present)
Monterey County (1850 - Present)
Napa County (1850 - Present)
Nevada County (1851 - Present)
Orange County (1889 - Present)
Pautah County Proposed (1852 - 1852)
Placer County (1851 - Present)
Plumas County (1854 - Present)
Riverside County (1893 - Present)
Sacramento County (1850 - Present)
San Benito County (1874 - Present)
San Bernardino County (1853 - Present)
San Diego County (1850 - Present)
San Francisco County (1850 - Present)
San Joaquin County (1850 - Present)
San Luis Obispo County (1850 - Present)
San Mateo County (1856 - Present)
Santa Barbara County (1850 - Present)
Santa Clara County (1850 - Present)
Shasta County (1850 - Present)
Sierra County (1852 - Present)
Siskiyou County (1852 - Present)
Solano County (1850 - Present)
Sonoma County (1850 - Present)
Stanislaus County (1854 - Present)
Sutter County (1850 - Present)
Tehama County (1856 - Present)
Trinity County (1850 - Present)
Tulare County (1852 - Present)
Tuolumne County (1850 - Present)
Ventura County (1873 - Present)
Yolo County (1850 - Present)
Yuba County (1850 - Present)