San Diego ( SAN dee-AY-goh; Spanish: [san ˈdjeɣo]) is a city on the Pacific coast of Southern California, next to the Mexican 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 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.
San Diego's name can be traced back to the 17th century when Spanish explorer Sebastián Vizcaíno bestowed it upon the area in 1602. He named the bay and the surrounding area "San Diego de Alcalá" in honor of Saint Didacus of Alcalá.
Prior to the Spanish establishment of San Diego, the Kumeyaay town was called Kosa'aay, meaning "drying out place" in the Kumeyaay language. After the establishment of San Diego, the Kumeyaay called town and city Tepacul Watai, meaning "Stacked Big". Luiseño speakers in the North County region called it Pushuyi.
What has been referred to as the San Dieguito complex was established in the area at least 9,000 years ago. The Kumeyaay may have culturally evolved from this complex or migrated into the area around 1000 C.E. Archaeologist Malcolm Rogers hypothesized that the early cultures of San Diego were separate from the Kumeyaay, but this claim is disputed. Rogers later reevaluated his claims, yet they were influential in shaping historical tellings of early San Diego history.
The Kumeyaay established villages scattered across the region, including the village of Kosa'aay which was the Kumeyaay village that the future settlement of San Diego would stem from in today's Old Town. The village of Kosa'aay was made up of thirty to forty families living in pyramid-shaped housing structures and was supported by a freshwater spring from the hillsides.
The first European to visit the region was explorer Juan Rodríguez Cabrillo. Sailing his flagship San Salvador from Navidad, New Spain, Cabrillo claimed the bay for the Spanish Empire in 1542, and named the site "San Miguel". In November 1602, Sebastián Vizcaíno surveyed the harbor and what are now Mission Bay and Point Loma and named the area for the Catholic Saint Didacus, a Spaniard more commonly known as San Diego de Alcalá.
The permanent European colonization of both California and San Diego began in 1769 with the arrival of four contingents of Spaniards from New Spain and the Baja California peninsula. Two seaborne parties reached San Diego Bay: the San Carlos, under Vicente Vila and including as notable members the engineer and cartographer Miguel Costansó and the soldier and future governor Pedro Fages, and the San Antonio, under Juan Pérez. An initial overland expedition to San Diego from the south was led by the soldier Fernando Rivera and included the Franciscan missionary, explorer, and chronicler Juan Crespí, followed by a second party led by the designated governor Gaspar de Portolá and including the mission president Junípero Serra.
In May 1769, Portolà established the Presidio of San Diego on a hill near the San Diego River above the Kumeyaay village of Cosoy, which would later become incorporated into the Spanish settlement, making it the first settlement by Europeans in what is now the state of California. In July of the same year, Mission San Diego de Alcalá was founded by Franciscan friars under Serra. The mission became a site for a Kumeyaay revolt in 1775, which forced the mission to relocate six miles (10 km) up the San Diego River. By 1797, the mission boasted the largest native population in Alta California, with over 1,400 neophytes living in and around the mission proper. Mission San Diego was the southern anchor in Alta California of the historic mission trail El Camino Real. Both the Presidio and the Mission are National Historic Landmarks.
In 1821, Mexico won its independence from Spain, and San Diego became part of the Mexican territory of Alta California. In 1822, Mexico began its attempt to extend its authority over the coastal territory of Alta California. The fort on Presidio Hill was gradually abandoned, while the town of San Diego grew up on the level land below Presidio Hill. The Mission was secularized by the Mexican government in 1834, and most of the Mission lands were granted to former soldiers. The 432 residents of the town petitioned the governor to form a pueblo, and Juan María Osuna was elected the first alcalde ("municipal magistrate"). Beyond the town, Mexican land grants expanded the number of California ranchos that modestly added to the local economy.
However, San Diego had been losing population throughout the 1830s due to increasing tension between the settlers and the indigenous Kumeyaay. In 1838 the town lost its pueblo status because its size dropped to an estimated 100 to 150 residents. The ranchos in the San Diego region faced Kumeyaay raids in the late 1830s and the town itself faced raids in the 1840s.
Americans gained an increased awareness of California and its commercial possibilities from the writings of two countrymen involved in the hide and tallow trade, which was often officially forbidden to foreigners but economically significant, with San Diego serving as a major port and the only one with an adequate harbor: William Shaler's "Journal of a Voyage Between China and the North-Western Coast of America, Made in 1804" and Richard Henry Dana's more substantial and convincing account, of his 1834–36 voyage, Two Years Before the Mast.
In 1846, the United States went to war against Mexico and sent a naval and land expedition to conquer Alta California. At first, they had an easy time of it, capturing the major ports including San Diego, but the Californios in southern Alta California struck back. Following the successful revolt in Los Angeles, the American garrison at San Diego was driven out without firing a shot in early October 1846. Mexican partisans held San Diego for three weeks until October 24, 1846, when the Americans recaptured it. For the next several months the Americans were blockaded inside the pueblo. Skirmishes occurred daily and snipers shot into the town every night. The Californios drove cattle away from the pueblo hoping to starve the Americans and their Californio supporters out. On December 1, the American garrison learned that the dragoons of General Stephen W. Kearney were at Warner's Ranch. Commodore Robert F. Stockton sent a mounted force of fifty under Captain Archibald Gillespie to march north to meet him. Their joint command of 150 men, returning to San Diego, encountered about 93 Californios under Andrés Pico.