California is a state on the West Coast of the United States, along the Pacific Ocean. It is bordered by Oregon to the north, Nevada to the east, Arizona to the southeast, and, to the south, the Mexican state of Baja California. California is the most populous U.S. state.Its four largest cities are Los Angeles, San Diego, San Jose, and San Francisco.The state is home to eight of the nation's fifty largest cities. It is known for its varied climate and geography as well as its diverse population. The area known as Alta California was colonized by the Spanish Empire beginning in the late 18th century. It and the rest of Mexico became an independent republic in 1821. In 1846, California broke away from Mexico, and, after the Mexican-American War, Mexico ceded California to the United States. It became the 31st state admitted to the United States on September 9, 1850.