After the Mexican–American War, the American portion became the Diocese of Monterey in California, while the Mexican portion was eventually reorganized into the Diocese of Tijuana.
[1] Pope Gregory XVI set up the Diocese of California with the papal bull Apostolicam sollicitudinem of 27 April 1840.
He set the episcopal residence at San Diego and made the diocese a suffragan of the Archdiocese of Mexico City.
[2] After the Mexican–American War, Alta California became United States territory and the Holy See divided the American diocese into US and Mexican sections.
On 20 November 1849, with the episcopal residence moved to Monterey, a more central position for the new diocese, the bishopric was formally suppressed, with two successor jurisdictions: The Residential Ordinaries were: The diocese was nominally restored as Latin titular bishopric of California or Both Californias in English, Ambas Californias in Spanish, or Californiensis in Latin.