San Diego, Spanish for ‘Saint Didacus is a city in the U.S. state of California on the coast of the Pacific Ocean and immediately adjacent to the Mexican border. With an estimated population of 1,423,851 as of July 1, 2019, San Diego is the eighth most populous city in the United States and second most populous in California (after Los Angeles).
 
The city is the county seat of San Diego County, the fifth most populous county in the United States, with 3,338,330 estimated residents as of 2019. The city is known for its mild year-round climate, natural deep-water harbor, extensive beaches and parks, long association with the United States Navy and Marine Corps, and recent emergence as a healthcare and biotechnology development center.