The Presidio of San Francisco is a park and former U.S. Army post on the northern tip of the San Francisco Peninsula in San Francisco, California, and is part of the Golden Gate National Recreation Area. It had been a fortified location since September 17, 1776, when New Spain established the presidio to gain a foothold in Alta California and the San Francisco Bay. It passed to Mexico in 1820, which in turn passed it to the United States in 1848.