Population of Counties in California (2020)

Not surprisingly, California's Los Angeles County 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 2020 Population Growth Since 2010
Los Angeles County10,105,5002.88%
San Diego County3,343,3607.74%
Orange County3,185,9705.62%
Riverside County2,450,76011.31%
San Bernardino County2,171,6006.40%
Santa Clara County1,937,5708.48%
Alameda County1,666,75010.16%
Sacramento County1,540,9808.41%
Contra Costa County1,150,2209.28%
Fresno County994,4006.69%
Kern County896,7646.62%
San Francisco County883,3059.65%
Ventura County850,9673.13%
San Mateo County769,5456.92%
San Joaquin County752,6609.53%
Stanislaus County549,8156.73%
Sonoma County499,9423.13%
Tulare County465,8615.16%
Solano County446,6107.89%
Santa Barbara County446,5275.25%
Monterey County435,5944.61%
Placer County393,14912.32%
San Luis Obispo County284,0105.26%
Merced County274,7657.02%
Santa Cruz County274,2554.21%
Marin County259,6662.67%
Butte County231,2565.14%
Yolo County220,4089.61%
El Dorado County190,6785.27%
Imperial County181,8274.06%
Shasta County180,0401.56%
Madera County157,6724.41%
Kings County151,366-0.67%
Napa County139,4171.91%
Humboldt County136,3731.02%
Nevada County99,6960.92%
Sutter County96,8072.17%
Mendocino County87,606-0.22%
Yuba County78,0417.87%
Lake County64,382-0.55%
Tehama County63,9160.55%
San Benito County61,53710.84%
Tuolumne County54,539-1.18%
Calaveras County45,6020.29%
Siskiyou County43,724-2.70%
Amador County39,3833.96%
Lassen County30,802-11.57%
Glenn County28,047-0.28%
Del Norte County27,828-2.59%
Colusa County21,6270.89%
Plumas County18,804-5.57%
Inyo County17,987-2.84%
Mariposa County17,471-4.41%
Mono County14,250-0.05%
Trinity County12,535-8.86%
Modoc County8,777-9.51%
Sierra County2,987-7.26%
Alpine County1,101-5.17%