Population of Counties in California (2020)

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 2020 Population Growth Since 2010
Los Angeles County10,079,0002.61%
San Diego County3,379,1608.89%
Orange County3,198,0006.01%
Riverside County2,517,83014.36%
San Bernardino County2,208,4008.21%
Santa Clara County1,945,9408.95%
Alameda County1,684,00011.30%
Sacramento County1,567,49010.28%
Contra Costa County1,160,92010.29%
Fresno County1,010,1208.37%
Kern County912,3168.47%
San Francisco County891,58310.68%
Ventura County851,2973.17%
San Joaquin County772,94812.49%
San Mateo County771,0197.13%
Stanislaus County558,9118.49%
Sonoma County493,3341.77%
Tulare County471,3896.41%
Solano County452,0769.21%
Santa Barbara County448,3695.69%
Monterey County435,8284.67%
Placer County408,31716.65%
San Luis Obispo County286,3546.13%
Merced County281,6159.69%
Santa Cruz County272,5553.57%
Marin County259,5482.63%
Butte County235,3547.01%
Yolo County224,47211.63%
El Dorado County194,5907.43%
Imperial County182,3334.35%
Shasta County181,0422.12%
Madera County161,2086.76%
Kings County154,7061.53%
Napa County137,4790.49%
Humboldt County136,0650.79%
Nevada County100,0821.31%
Sutter County97,5452.95%
Mendocino County87,424-0.43%
Yuba County80,57311.37%
Lake County64,8220.13%
Tehama County64,3121.18%
San Benito County64,21315.66%
Tuolumne County55,5390.63%
Calaveras County45,5220.12%
Siskiyou County43,604-2.97%
Amador County41,0478.35%
Lassen County30,160-13.41%
Del Norte County28,6280.21%
Glenn County28,2290.37%
Colusa County21,5310.44%
Plumas County18,932-4.93%
Inyo County18,065-2.41%
Mariposa County17,539-4.04%
Mono County14,2800.16%
Trinity County12,153-11.64%
Modoc County8,635-10.97%
Sierra County2,943-8.63%
Alpine County1,061-8.61%