San Diego

San Diego (/ˌsæn diˈeɪɡoʊ/ ^ⓘ SAN dee-AY-goh; Spanish: [san ˈdjeɣo]) is a city on the Pacific coast of Southern California, adjacent to the Mexico–United States border. It is the eighth-most populous city in the U.S. and second-most populous city in California with a population of over 1.4 million, while the San Diego metropolitan area with over 3.3 million residents is the 18th-largest metropolitan area in the country. San Diego is the county seat of San Diego County. It is known for its mild Mediterranean climate, extensive beaches and parks, long association with the United States Navy, and recent emergence as a wireless, electronics, healthcare, and biotechnology development center.

Historically home to the Kumeyaay people, San Diego has been referred to as the Birthplace of California, as it was the first site visited and settled by Europeans on what is now the West Coast of the United States. 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. California was ceded to the U.S. in 1848 following the Mexican–American War and was admitted as the 31st state in 1850.

The largest sectors of the economy of San Diego include military and defense-related activities, tourism, international trade, research, and manufacturing. The city is home to several universities, including UC San Diego, San Diego State University, and the University of San Diego. San Diego is the economic center of the San Diego–Tijuana region, the second-most populous transborder metropolitan area in the Western Hemisphere, home to an estimated five million people as of 2022. The primary border crossing between San Diego and Tijuana, the San Ysidro Port of Entry, is the busiest international land border crossing in the world outside of Asia (fourth-busiest overall). San Diego International Airport (SAN) is the busiest single-runway airport in the United States.