Alpine is a census-designated place (CDP) in the Cuyamaca Mountains of San Diego County, California, United States. Alpine had a population of 14,696 at the 2020 census, up from 14,236 at the 2010 census. The town is largely surrounded by Cleveland National Forest and borders two reservations of the Kumeyaay, Viejas and Sycuan tribes, and the rural unincorporated areas around the city of El Cajon.