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 Density (mi²)
Los Angeles County9,969,5101.49%13,488.85
San Diego County3,347,2707.86%4,528.89
Orange County3,175,1305.31%4,295.98
Riverside County2,520,06014.47%3,409.67
San Bernardino County2,206,7508.13%2,985.76
Santa Clara County1,918,8807.44%2,596.26
Alameda County1,680,48011.07%2,273.71
Sacramento County1,578,68011.07%2,135.97
Contra Costa County1,159,54010.17%1,568.87
Fresno County1,013,4008.73%1,371.14
Kern County913,0908.57%1,235.42
San Francisco County883,2559.65%1,195.05
Ventura County841,7342.02%1,138.87
San Joaquin County781,46213.73%1,057.33
San Mateo County762,3575.93%1,031.48
Stanislaus County555,7287.88%751.91
Sonoma County485,7220.20%657.19
Tulare County469,4075.97%635.11
Solano County451,4799.06%610.86
Santa Barbara County447,9375.59%606.06
Monterey County434,2834.30%587.59
Placer County410,32717.23%555.18
Merced County284,73810.91%385.25
San Luis Obispo County282,6254.75%382.39
Santa Cruz County271,9573.35%367.96
Marin County257,1541.68%347.93
Yolo County221,26410.04%299.37
El Dorado County197,0378.78%266.59
Butte County196,880-10.49%266.38
Shasta County180,8222.00%244.65
Imperial County180,5993.37%244.35
Madera County158,2174.79%214.07
Kings County156,0562.42%211.15
Napa County135,654-0.81%183.54
Humboldt County134,186-0.61%181.56
Nevada County100,2491.48%135.64
Sutter County98,2173.66%132.89
Mendocino County85,445-2.68%115.61
Yuba County80,89011.81%109.45
Tehama County67,2165.75%90.94
San Benito County65,49017.97%88.61
Lake County64,524-0.33%87.30
Tuolumne County54,660-0.96%73.96
Calaveras County46,3191.87%62.67
Siskiyou County43,517-3.16%58.88
Amador County40,4466.76%54.72
Lassen County30,483-12.48%41.24
Glenn County29,2453.97%39.57
Del Norte County27,956-2.14%37.82
Colusa County21,8051.72%29.50
Plumas County18,939-4.90%25.62
Inyo County18,225-1.55%24.66
Mariposa County16,799-8.09%22.73
Mono County14,5261.89%19.65
Trinity County11,721-14.79%15.86
Modoc County8,923-7.95%12.07
Sierra County3,021-6.18%4.09
Alpine County1,2094.13%1.64