Today’s California counties did not always exist in the present form. They went through many different changes in the space of a few short years.

The 27 Original Counties Of California

A committee of California’s first constitutional convention was convened on January 4, 1850. At this meeting, it was suggested that California be split into 18 counties.

The 18 counties were Benicia, Butte, Fremont, Los Angeles, Mariposa, Monterey, Mt. Diablo, Oro, Redding, Sacramento, San Diego, San Francisco, San Joaquin, San Jose, San Luis Obispo, Santa Barbara, Sonoma and Sutter Counties

The committee later suggested some other changes and on February 18, 1850, the following 9 counties were added to the 18 counties, making a total of 27 counties:

The 9 counties were Branciforte, Calaveras, Coloma, Colusi, Marin, Mendocino, Napa, Trinity and Yuba Counties

The committee also changed the names of several of the original counties at that time.

Those changes were Benicia to El Dorado, Fremont to Yola, Mt. Diablo to Contra Costa, San Jose to Santa Clara, Oro to Tuolumne, Redding to Shasta

This meant that, as of February 18, 1850, the 27 counties in California were:

Branciforte, Butte, Calaveras, Colusi, Contra Costa, El Dorado, Los Angeles, Marin, Mariposa, Mendocino, Monterey, Napa, Sacramento, San Diego, San Francisco, San Joaquin, San Luis Obispo, Santa Barbara, Santa Clara, Shasta, Solano, Sonoma, Sutter, Trinity, Tuolumne, Yola, Yuba

Then, a little later in 1850, some legislature was adopted that caused some of the county names to change yet again. Branciforte became Santa Cruz and Colusi became Colusa. Yola, meanwhile, was changed to Yolo.

However, 32 more counties were created in the state after 1850. Of the original 27, only Marin county stayed exactly as it was, neither losing nor gaining land.

Of the 32 created later, only 7 stayed as they were upon their creation. Those 7 are: Alameda, Alpine, Imperial, Madera, Modoc, Orange, Riverside

The State of California entered the union as the 31st state by Congress on September 9, 1850, as part of the Compromise of 1850.

California Counties Today

Today, California is divided into 58 counties.  States bordering California are Nevada, Oregon and Arizona.

California has counties that no longer are in existence. A lot of these counties were established and disbanded within the 19th century; county borders have modified very little since 1900 in the vast most of states.

Fun Facts about California Counties

• California was first divided into 27 counties on February 18, 1850.
• These were further sub-divided to form 16 additional counties by 1860.
• Another 14 counties formed through further subdivision from 1861 to 1893.

Counties by Name

More California counties are named for saints than in any other state.

Counties by Year

• Branciforte, Butte, Calaveras, Colusi, Contra Costa, El Dorado, Los Angeles, Marin, Mariposa, Mendocino, Monterey, Napa, Sacramento, San Diego, San Francisco, San Joaquin, San Luis Obispo, Santa Barbara, Santa Clara, Shasta, Solano, Sonoma, Sutter, Trinity, Tuolumne, Yola and Yuba Counties was the 27 original counties created as of February 18, 1850.
• Imperial County was the last county created on August 7, 1907.

County Size Facts

• San Francisco County (47 sq mi) is the largest county in California.
• San Bernardino County (20,062 sq mi) is the smallest county in California.

County Population Facts

• Alpine County (1,120) is the least populated county in California.
• Los Angeles County (10,163,507) is the most populated county in California.

California City Facts

California’s 10  largest (2010) cities are:

1. Los Angeles (3,792,621) is in Los Angeles County
2. San Diego (1,301,617) is in San Diego County
3. San Jose (945,942) is in Santa Clara County
4. San Francisco (805,235) is in San Francisco County
5. Fresno (494,665) is in Fresno County
6. Sacramento (466,488) is in Sacramento County
7. Long Beach (462,257) is in Los Angeles County
8. Oakland (390,724) is in Alameda County
9. Bakersfield (347,483) is in Kern County
10. Anaheim (336,265) is in Orange County

Boundary Changes of California Counties from 1850-1925

This Interactive Map of California Counties show the historical boundaries, names, organization, and attachments of every county, extinct county and unsuccessful county proposal from 1850 to 1925.

Many of the county boundaries have also experienced small changes over the years. The original county boundaries tended to follow the geography of the land, often being established along mountain ridges and similar natural features.

These days, many of those boundaries have been altered to run along either section lines or township lines.

List of California Counties

List of Old Former / Extinct California Counties

California contains some counties that no longer exist because they were discontinued, renamed or merged with another county. These are important for genealogy research purposes.

The below counties formerly within the area of the State of California no longer exist: 

Branciforte County, California

Branciforte County was one of the original 27 counties adopted by statutes of 1850, but soon after that the legislature changed the name to Santa Cruz County.

Coloma County, California

Coloma County was a county proposed by a committee of the California Constitutional Convention. Before the statute was adopted, the legislature changed the name to El Dorado County.

Coso County, California

Coso County was approved by the State Legislature which designated territory in Mono County and Tulare County to be in the new county with the county seat at Bend City.

Coso County, however, was never organized. In 1866 substantially the same territory was created as Inyo County.

Fremont County, California

Was a county proposed by a committee of the California Constitutional Convention. Before the statute was adopted, the legislature changed the name to Yola County and later changed the name to Yolo County.

Coloma County, California

Created in 1851 from the northern half of Trinity County. In 1857 Klamath County lost significant territory to the newly formed Del Norte County.

In 1875 Klamath County was abolished and its territory was divided between Humboldt County and Siskiyou County.

Mount Diablo County, California

Was a county proposed by a committee of the California Constitutional Convention. Before the statute was adopted, the legislature changed the name to Contra Costa County.

Oro County, California

Was a county proposed by a committee of the California Constitutional Convention. Before the statute was adopted, the legislature changed the name to Tuolumne County.

Coloma County, California

Created in 1852, an act to be effective when the United States Congress ceded to the State of California the territory described, in what is now the State of Nevada. The County seat was to be Carsonville. California never acquired the territory and the act creating the county was repealed in 1859.

Redding County, California

Was a county proposed by a committee of the California Constitutional Convention. Before the statute was adopted, the legislature changed the name to Shasta County.

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