Juan Cabrillo discovered California by entering San Diego Bay in 1542. It was the feast day of Saint Michael the Archangel.

Cabrillo named the port San Miguel in his honor. It was another 60 years before Spaniards revisited San Miguel.

Explorer Vizcaino arrived at the port in 1602. Vizcaino, in disregard of orders, changed the name of the port to "San Diego", claiming Cabrillo's calculations of latitude were incorrect and he could find no San Miguel.

In 1769, Father Serra dedicated the first Mission as Mission San Diego de Alcala, after Franciscan friar, Saint Didacus (translated to San Diego), who was sainted by Pope Sixtus V in 1588.