The city is located on the site of the first European settlement in California. Juan Rodríguez Cabrillo sailed into San Diego Bay in 1542 and claimed the land for Spain. In 1769 Junípero Serra, a Franciscan missionary, established Mission San Diego de Alcalá and dedicated the Presidio, the first Spanish fort in California. By 1830 most of the people were living in what is now Old Town. It was under Mexican jurisdiction from 1822, when Mexico won independence from Spain, until 1846, when it was captured by a U.S. naval force. The city's population surged when the Santa Fe RR arrived in 1884.
San Diego became an important U.S. naval base during World War I; later, other branches of the military established bases there. In the 1950s, this concentration of military installations gave rise to San Diego's aerospace industry. The diversification of San Diego's economic base in the latter part of the 20th cent. contributed to its rapid growth. An urban revitalization effort begun in the 1980s included Horton Plaza, an expansive shopping mall that won acclaim for its dramatic architecture, as well as the inauguration of a trolley system.