Population of Counties in California (2018)

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 3,317,200 and a growth rate of 6.88%, while neighboring Orange County has 3,177,703 residents and a growth rate of 5.32%.

The smallest county in California is Alpine County, with its population of just 1,057. This total represents a decrease of 8.96% since the last census. Sierra County and Modoc County follow, with populations of 2,964 and 8,941, respectively, and negative growth rates of 7.98% and 7.82%. 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 an increase of 9.24% – 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 30,944 residents representing a significant decrease of 11.16%.

Name 2018 Population Growth Since 2010
Los Angeles County10,163,5073.45%
San Diego County3,337,6857.54%
Orange County3,190,4005.74%
Riverside County2,423,26610.05%
San Bernardino County2,157,4045.69%
Santa Clara County1,938,1538.49%
Alameda County1,663,1909.90%
Sacramento County1,530,6157.66%
Contra Costa County1,147,4398.99%
Fresno County989,2556.12%
Kern County893,1196.18%
San Francisco County884,3639.75%
Ventura County854,2233.50%
San Mateo County771,4107.16%
San Joaquin County745,4248.46%
Stanislaus County547,8996.34%
Sonoma County504,2174.00%
Tulare County464,4934.84%
Santa Barbara County448,1505.61%
Solano County445,4587.58%
Monterey County437,9075.15%
Placer County386,16610.32%
San Luis Obispo County283,4055.04%
Santa Cruz County275,8974.82%
Merced County272,6736.19%
Marin County260,9553.17%
Butte County229,2944.24%
Yolo County219,1168.96%
El Dorado County188,9874.33%
Imperial County182,8304.61%
Shasta County179,9211.49%
Madera County156,8903.88%
Kings County150,101-1.51%
Napa County140,9733.05%
Humboldt County136,7541.29%
Nevada County99,8141.04%
Sutter County96,6481.99%
Mendocino County88,0180.25%
Yuba County77,0316.47%
Lake County64,246-0.77%
Tehama County63,9260.57%
San Benito County60,3108.60%
Tuolumne County54,248-1.70%
Calaveras County45,6700.44%
Siskiyou County43,853-2.42%
Amador County38,6261.96%
Lassen County31,163-10.53%
Glenn County28,094-0.13%
Del Norte County27,470-3.84%
Colusa County21,8051.64%
Plumas County18,742-5.89%
Inyo County18,026-2.65%
Mariposa County17,569-3.89%
Mono County14,168-0.25%
Trinity County12,709-7.56%
Modoc County8,859-8.66%
Sierra County2,999-6.89%
Alpine County1,120-3.53%