In 1850, two years after the Mexican Cession, the Diocese of Alta and Baja California was split between the American and Mexican territories, and San Jose became a part of the Diocese of Monterey. In 1853, the northern half of the county became part of the Archdiocese of San Francisco, while the areas around Gilroy and Morgan Hill remained in the Diocese of Monterey. In 1922 the American Catholic Church decided to use county boundaries for dioceses, and the southern half of the county was transferred to the Archdiocese of San Francisco.