California Counties

This article helps you quickly understand California counties—what they are, how they differ, and why they matter—before giving you a complete, sortable-style table of every county with its population, area, and county seat. Use it to compare regions, plan moves, or get context for local services anywhere in the state.

Understand How California Counties Actually Work

Counties in California are the local arms of the state, created to deliver day-to-day public services such as elections, jails, public health, roads in unincorporated areas, and social services. Legally, a county is a political subdivision of the State of California and exercises powers granted by the state. Most are general law counties, which follow state statutes for their structure and authorities. Fourteen counties operate under a home-rule charter, which allows limited flexibility in governance: Alameda, Butte, El Dorado, Fresno, Los Angeles, Orange, Placer, Sacramento, San Bernardino, San Diego, San Francisco, San Mateo, Santa Clara, and Tehama. Regardless of type, each county has a board of supervisors, countywide elected officials (such as sheriff, district attorney, assessor), and numerous service departments.

Trace the Formation of the 58 California Counties

California began with 27 original counties in 1850 as statehood arrived, then added more through subdivision during the Gold Rush and state-building decades. Sixteen additional counties were formed by 1860, another fourteen between 1861 and 1893, and the most recent, Imperial County, was created in 1907. The county map has been tweaked on paper—some proposed counties never materialized (for example, Mojave County or Mission County)—and several historic entities were dissolved or reassigned (including Klamath and Roop) as boundaries were clarified. Today’s 58-county framework has remained stable for over a century, anchoring regional identity and service delivery from the Oregon line to the Mexican border.

Size and Scale: Spot the Extremes Across California Counties

California’s county geography stretches from compact coastal urban cores to vast inland deserts and mountains. San Bernardino County is the largest county in the contiguous United States at 20,062 square miles, spanning Mojave Desert communities and High Desert city clusters. On the other end, the consolidated City and County of San Francisco covers just 47 square miles, proving that economic and cultural impact don’t require sheer acreage. Population extremes also define the landscape: Los Angeles County is the most populous county in the nation—home to nearly 10 million residents—while Alpine County has just over a thousand people, trading density for alpine solitude. Between those poles sit fast-growing inland hubs (Riverside, San Bernardino, Sacramento), established tech and research anchors (Santa Clara, San Mateo, Alameda), agricultural powerhouses (Fresno, Kern, Tulare), and coastal destinations (San Diego, Santa Barbara, Monterey).

Names Tell Stories: Saints, Landscapes, and Native Languages

County names reflect California’s layered history—Spanish missions, Native languages, explorers, and the Gold Rush. Many counties carry saintly names through mission heritage (e.g., San Diego, San Mateo, Santa Barbara, Santa Clara). Others capture natural features: Plumas (feathers, for the Feather River), Lake (for Clear Lake), El Dorado (Gold Rush lore), or Riverside (on the Santa Ana River). Some honor historical figures (Marin, Kern, Glenn), while others preserve Native words and peoples (Yolo, Sonoma, Modoc, Mono). These names aren’t just labels—they encode settlement patterns, faith traditions, and the state’s unmatched physical diversity.

What Counties Deliver: Everyday Services that Touch Residents

When you vote, request vital records, use a branch library outside a city, need behavioral health services, or drive rural roads—county government is often in the background. Counties administer public health programs, child welfare, courts support, property tax assessment, land-use planning in unincorporated communities, and emergency management. In metropolitan areas, county and city roles overlap; in rural regions, the county may be the main public service provider. Knowing your county seat (the administrative center) helps you find the right office for permits, records, and hearings.

California Counties Ranked by Population (with County Seat and Area)

County	Population	Area (sq mi)	County Seat
Los Angeles County	9,757,179	4,060	Los Angeles
San Diego County	3,298,799	4,204	San Diego
Orange County	3,170,435	948	Santa Ana
Riverside County	2,529,933	7,208	Riverside
San Bernardino County	2,214,281	20,062	San Bernardino
Santa Clara County	1,926,325	1,291	San Jose
Alameda County	1,649,060	738	Oakland
Sacramento County	1,611,231	966	Sacramento
Contra Costa County	1,172,607	720	Martinez
Fresno County	1,024,125	5,963	Fresno
Kern County	922,529	8,142	Bakersfield
Ventura County	835,427	1,846	Ventura
San Francisco	827,526	47	San Francisco
San Joaquin County	816,108	1,399	Stockton
San Mateo County	742,893	449	Redwood City
Stanislaus County	556,972	1,495	Modesto
Sonoma County	485,375	1,576	Santa Rosa
Tulare County	483,546	4,824	Visalia
Solano County	455,101	828	Fairfield
Santa Barbara County	444,500	2,738	Santa Barbara
Placer County	433,822	1,407	Auburn
Monterey County	436,251	3,322	Salinas
Merced County	296,774	1,929	Merced
San Luis Obispo County	281,843	3,304	San Luis Obispo
Santa Cruz County	262,406	446	Santa Cruz
Marin County	256,400	520	San Rafael
Yolo County	225,251	1,012	Woodland
Butte County	208,334	1,640	Oroville
El Dorado County	192,823	1,712	Placerville
Imperial County	181,724	4,175	El Centro
Shasta County	181,121	3,786	Redding
Madera County	165,432	2,138	Madera
Kings County	154,913	1,390	Hanford
Napa County	132,727	754	Napa
Humboldt County	132,380	3,573	Eureka
Nevada County	102,195	958	Nevada City
Sutter County	98,545	603	Yuba City
Yuba County	87,469	630	Marysville
Mendocino County	89,175	3,509	Ukiah
San Benito County	69,159	1,389	Hollister
Lake County	67,764	1,258	Lakeport
Tehama County	64,451	2,951	Red Bluff
Tuolumne County	53,893	2,236	Sonora
Calaveras County	46,505	1,020	San Andreas
Amador County	42,026	606	Jackson
Siskiyou County	42,498	6,287	Yreka
Glenn County	28,304	1,315	Willows
Lassen County	28,340	4,558	Susanville
Del Norte County	27,009	1,008	Crescent City
Colusa County	22,074	1,151	Colusa
Plumas County	18,834	2,554	Quincy
Inyo County	18,485	10,192	Independence
Mariposa County	17,048	1,451	Mariposa
Trinity County	15,642	3,179	Weaverville
Mono County	12,991	3,044	Bridgeport
Modoc County	8,491	3,944	Alturas
Sierra County	3,113	953	Downieville
Alpine County	1,099	739	Markleeville