The San Francisco area has been populated since prehistoric times, but the first official discovery by Europeans was a Spanish expedition led by Don Gaspar de Cortola in 1769. At that time the main inhabitants were the Ohlone people, a Native American group.

In 1776 another explorer, Juan Batista de Anza, began work on the Presidio of San Fransisco, a military centre. This is usually seen as the real founding of the city. A Christian mission was also built nearby, again with the name of San Francisco.

In 1835, when the Bay area was under Mexican control, the beginnings of a town were started by two men, Alcado Francisco de Haro and William Richardson. In 1847 the town was officially named San Francisco. At this time it was still very small, but as the Gold Rush got under way it soon grew, and by 1860 it was a rich and well-defended city.