
Below are the 58 California counties sorted by population from largest to smallest. The population data are from the 2021 American Community Survey.
| Rank | County | Population |
|---|
| 1 | Los Angeles County | 10,019,635 |
| 2 | San Diego County | 3,296,317 |
| 3 | Orange County | 3,182,923 |
| 4 | Riverside County | 2,409,331 |
| 5 | San Bernardino County | 2,171,071 |
| 6 | Santa Clara County | 1,932,022 |
| 7 | Alameda County | 1,673,133 |
| 8 | Sacramento County | 1,571,767 |
| 9 | Contra Costa County | 1,161,643 |
| 10 | Fresno County | 1,003,150 |
| 11 | Kern County | 905,644 |
| 12 | San Francisco County | 865,933 |
| 13 | Ventura County | 845,255 |
| 14 | San Joaquin County | 771,406 |
| 15 | San Mateo County | 762,488 |
| 16 | Stanislaus County | 550,842 |
| 17 | Sonoma County | 492,498 |
| 18 | Tulare County | 470,999 |
| 19 | Solano County | 451,432 |
| 20 | Santa Barbara County | 447,651 |
| 21 | Monterey County | 438,953 |
| 22 | Placer County | 400,330 |
| 23 | San Luis Obispo County | 282,771 |
| 24 | Merced County | 279,150 |
| 25 | Santa Cruz County | 272,138 |
| 26 | Marin County | 262,387 |
| 27 | Butte County | 217,884 |
| 28 | Yolo County | 216,703 |
| 29 | El Dorado County | 190,568 |
| 30 | Shasta County | 181,935 |
| 31 | Imperial County | 180,051 |
| 32 | Madera County | 156,304 |
| 33 | Kings County | 151,887 |
| 34 | Napa County | 138,795 |
| 35 | Humboldt County | 137,014 |
| 36 | Nevada County | 102,090 |
| 37 | Sutter County | 99,080 |
| 38 | Mendocino County | 91,534 |
| 39 | Yuba County | 80,404 |
| 40 | Lake County | 67,749 |
| 41 | Tehama County | 65,345 |
| 42 | San Benito County | 63,329 |
| 43 | Tuolumne County | 55,243 |
| 44 | Calaveras County | 45,349 |
| 45 | Siskiyou County | 44,151 |
| 46 | Amador County | 40,095 |
| 47 | Lassen County | 32,949 |
| 48 | Glenn County | 28,675 |
| 49 | Del Norte County | 27,655 |
| 50 | Colusa County | 21,780 |
| 51 | Plumas County | 19,631 |
| 52 | Inyo County | 18,804 |
| 53 | Mariposa County | 17,225 |
| 54 | Trinity County | 15,818 |
| 55 | Mono County | 13,291 |
| 56 | Modoc County | 8,723 |
| 57 | Sierra County | 3,079 |
| 58 | Alpine County | 1,344 |
United States Census Bureau. B01001 SEX BY AGE, 2021 American Community Survey 5-Year Estimates. U.S. Census Bureau, American Community Survey Office. Web. 8 December 2022. http://www.census.gov/. |