San Diego. San Diego is a city on the Pacific Ocean coast of Southern California located immediately adjacent to the Mexico-United States border.
With a 2020 population of 1,386,932, it is the eighth-most populous city in the United States, the second-most populous city in California and the seat of San Diego County, the fifth-most populous county in the United States, with 3,286,069 estimated residents as of 2021. The city is known for its mild year-round Mediterranean climate, natural deep-water harbor, extensive beaches and parks, long association with the United States Navy, and recent emergence as a healthcare and biotechnology development center.
San Diego is the second-largest city in California after Los Angeles. Historically home to the Kumeyaay Native Americans, San Diego has been referred to as the Birthplace of California, since it was the first site visited and settled by Europeans on what is now the U.S.
West Coast. Upon landing in San Diego Bay in 1542, Juan Rodríguez Cabrillo claimed the area for Spain, forming the basis for the settlement of Alta California 200 years later.
The Presidio and Mission San Diego de Alcalá, founded in 1769, formed the first European settlement in what is now California. In 1821, San Diego became part of the newly declared Mexican Empire, which reformed as the First Mexican Republic two years later. California was conquered by the U.S. in 1848