California is a census-designated place and community in St. Mary's County, Maryland, United States. The population was 11,857 at the 2010 census, an increase of 27.4% from the 2000 census. California has been growing with the spread of population from the older adjacent community of Lexington Park and the growth in both technology-related and defe…California is a census-designated place and community in St. Mary's County, Maryland, United States. The population was 11,857 at the 2010 census, an increase of 27.4% from the 2000 census. California has been growing with the spread of population from the older adjacent community of Lexington Park and the growth in both technology-related and defense-related jobs at the Patuxent River Naval Air Station. There are department stores and numerous shopping centers situated along Maryland Highway 235. Maryland Route 4 crosses Highway 235 in California, providing access to the wide Governor Thomas Johnson Bridge and the popular weekend resort town of Solomons on its opposite side. Bridge-bound traffic is notorious for backing up during rush hour.