Imperial Beach is a residential beach city in San Diego County, California, with a population of 26,137 at the 2020 United States census, down from 26,324 at the 2010 census. The city is the southernmost city in California and the West Coast of the United States. It is in the South Bay area of San Diego County, 14.1 mi south of downtown San Diego and 5 mi northwest of downtown Tijuana, Mexico.