San Diego County, California, USA
County or equivalent
Location overview
San Diego County is located in the southwestern corner of California, bordered by Mexico, the Pacific Ocean, and Riverside, Orange and Imperial counties. The county includes 18 incorporated cities, led by San Diego, as well as a large unincorporated area containing suburban, rural, mountain and desert communities. Its landscape extends from about 70 miles of Pacific coastline across inland valleys and mountains to the Colorado Desert. San Diego County had an estimated population of 3,282,248 in 2025. County government provides regional health and social services, public safety, courts, elections and other services, while also acting as the local government for unincorporated communities.