California is the most populous state of the United States. Located on the Pacific coast of North America, it is bordered by Oregon, Nevada and Arizona in the United States, and Baja California in Mexico. The state's four largest cities are Los Angeles, San Diego, San Jose and San Francisco. California is known for its Mediterranean climate and ethnically diverse population. The state has 58 counties.
Inhabited by indigenous people for millennia, Alta California was first colonized by the Spanish Empire in 1769, and after Mexican independence in 1821, continued as part of Mexico. Following one brief week as the independent California Republic in 1846, and the conclusion of the Mexican-American war in 1848, California was annexed by the United States and was admitted to the Union as the thirty-first state on September 9, 1850.