San Diego is a major city in California, United States. It is in San Diego County, on the coast of the Pacific Ocean in Southern California, approximately 120 miles south of Los Angeles and immediately adjacent to the border with Mexico. With an estimated population of 1,406,630 as of July 1, 2016, San Diego is the eighth-largest city in the United States and second-largest in California. It is part of the San Diego–Tijuana conurbation, the second-largest transborder agglomeration between ...