California Counties by Population (2024)

There are 58 counties in California. 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%.