No, California was not "ceded" to the United States in 1848. California was actually acquired by the United States as a result of the Treaty of Guadalupe Hidalgo, which was signed on February 2, 1848, ending the Mexican-American War. Under the terms of the treaty, Mexico ceded California, along with other territories, to the United States in exchange for a payment of $15 million. California officially became a state in the United States on September 9, 1850.
