The Presidio of San Francisco is a former military base located in the northwest corner of the city. Its origins go back to 1776 when it was first established as a military post by the Spanish. From 1821 to 1846, it was under Mexican control, and from 1846 to 1994, it was an active U.S. Army base. It served in several wars, from the Civil War to Desert Storm in 1991, and many of the cannons, fortifications, and artillery displays can still be seen today. Crissy Field, the former airstrip for the military base, has been converted into a recreational field and habitat restoration area. In 1994, the base was deactivated and handed over to the National Park Service. The park has about 800 buildings set among the wooded area.
Former Army barracks have since been converted into housing, and many other historical buildings have become home for various commercial uses such as a private school, several non-profit organizations, the corporate headquarters for George Lucas, the Walt Disney museum, and a Sports Basement (a sporting goods store).
You can see the Presidio on a 1- or 2-Day Hop-on Hop-off San Francisco City Tour, a GoCar Tour, or by Renting a Bicycle.