San Diego /ˌsæn diːˈeɪɡoʊ/ is the eighth-largest city in the United States and second-largest city in California. The city is located on the coast of the Pacific Ocean in Southern California, immediately adjacent to the Mexican border. The birthplace of California, San Diego is known for its mild year-round climate, its natural deep-water harbor, and its long association with the U.S. Navy. The population was 1,301,617 at the 2010 census.