San Diego County is one of the original 27 counties, one of the two largest formed in 1850. Named after San Diego Bay, which had been rechristened by Vizcaino in 1602, in honor of the Franciscan, San Diego de Alcala de Henares, whose name was borne by his flagship. Territory which was once in San Diego County is now in Imperial, Inyo, Riverside and San Bernardino counties.

.........