Los Angeles, officially the City of Los Angeles and often known by its initials L.A., is the cultural, financial, and commercial center of Southern California. With a U.S. Census-estimated 2016 population of 3,976,322, it is the second most populous city in the United States (after New York City) and the most populous city in the state of California. Located in a large coastal basin surrounded on three sides by mountains reaching up to and over 10000ft, Los Angeles covers an area of about 469sqmi. The city is also the seat of Los Angeles County, the most populated county in the country. Los Angeles is the center of the Los Angeles metropolitan area, with 13,131,431 residents, and is part of the larger designated Los Angeles-Long Beach combined statistical area (CSA), the second most populous in the nation with a 2015 estimated population of 18.7 million.Historically home to the Chumash and Tongva, Los Angeles was claimed by Juan Rodríguez Cabrillo for Spain in 1542 along with the rest of what would become Alta California. The city was officially founded on September 4, 1781, by Spanish governor Felipe de Neve. It became a part of Mexico in 1821 following the Mexican War of Independence. In 1848, at the end of the Mexican–American War, Los Angeles and the rest of California were purchased as part of the Treaty of Guadalupe Hidalgo, thereby becoming part of the United States. Los Angeles was incorporated as a municipality on April 4, 1850, five months before California achieved statehood. The discovery of oil in the 1890s brought rapid growth to the city. The completion of the Los Angeles Aqueduct in 1913, delivering water from Eastern California, later assured the city's continued rapid growth.