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 the US and a bordering country after Detroit–Windsor, with a population of 4,922,723 people. The city is known for its mild year-round climate, natural deep-water harbor, extensive beaches, long association with the United States Navy, and recent emergence as a healthcare and biotechnology development center.San Diego has been called “the birthplace of California”. Historically home to the Kumeyaay people, it was the first site visited by Europeans on what is now the West Coast of the United States.