Population of Counties in California (2021)

Not surprisingly, California's Los Angeles County(/us-counties/ca/los-angeles-county-population) is the largest county in the state, as well as the nation, with a huge population of 10,150,558 that continues to grow – the most recent census shows that its population has increased by 3.32% since the last census. A number of other Californian counties also boast large populations, although they look small in comparison to Los Angeles County. San Diego County has a population of 3,337,685 and a growth rate of 7.8%, while neighboring Orange County has 3,190,400 residents and a growth rate of 6%.

The smallest county in California is Alpine County, with its population of just 1,120. This total represents a decrease of 4.7% since the last census count performed in 2010. Sierra County and Modoc County follow, with populations of 2,999 and 8,859, respectively, and negative growth rates of 7.4% and 8.5%. Many other counties have fewer than fifty thousand residents, such as Trinity County (12,839), Del Norte County (27,450), and Siskiyou County (43,511) – each of these counties also show negative growth rates. However, one smaller county, San Benito County (59,335) has increased its population by an impressive 6.85% since the last census.

Alameda County, with its sizeable population of 1,653,236, has shown the largest population growth, with a substantial increase of 10.1% – this can perhaps be attributed to its proximity to San Francisco. Indeed, San Francisco County also has a substantial population growth of 8.73% and 876,103 residents. Lassen County has the highest negative growth, with its 31,000 residents representing a significant decrease of 10.7%.

Name 2021 Population Growth Since 2010
Los Angeles County9,969,5101.49%
San Diego County3,347,2707.86%
Orange County3,175,1305.31%
Riverside County2,520,06014.47%
San Bernardino County2,206,7508.13%
Santa Clara County1,918,8807.44%
Alameda County1,680,48011.07%
Sacramento County1,578,68011.07%
Contra Costa County1,159,54010.17%
Fresno County1,013,4008.73%
Kern County913,0908.57%
San Francisco County883,2559.65%
Ventura County841,7342.02%
San Joaquin County781,46213.73%
San Mateo County762,3575.93%
Stanislaus County555,7287.88%
Sonoma County485,7220.20%
Tulare County469,4075.97%
Solano County451,4799.06%
Santa Barbara County447,9375.59%
Monterey County434,2834.30%
Placer County410,32717.23%
Merced County284,73810.91%
San Luis Obispo County282,6254.75%
Santa Cruz County271,9573.35%
Marin County257,1541.68%
Yolo County221,26410.04%
El Dorado County197,0378.78%
Butte County196,880-10.49%
Shasta County180,8222.00%
Imperial County180,5993.37%
Madera County158,2174.79%
Kings County156,0562.42%
Napa County135,654-0.81%
Humboldt County134,186-0.61%
Nevada County100,2491.48%
Sutter County98,2173.66%
Mendocino County85,445-2.68%
Yuba County80,89011.81%
Tehama County67,2165.75%
San Benito County65,49017.97%
Lake County64,524-0.33%
Tuolumne County54,660-0.96%
Calaveras County46,3191.87%
Siskiyou County43,517-3.16%
Amador County40,4466.76%
Lassen County30,483-12.48%
Glenn County29,2453.97%
Del Norte County27,956-2.14%
Colusa County21,8051.72%
Plumas County18,939-4.90%
Inyo County18,225-1.55%
Mariposa County16,799-8.09%
Mono County14,5261.89%
Trinity County11,721-14.79%
Modoc County8,923-7.95%
Sierra County3,021-6.18%
Alpine County1,2094.13%