What was once home to the native tribe known as the Ohlone, and functioning as guardian of the San Francisco Bay under Spanish, Mexican, and American flags, the Presidio has served as outpost as well as cultural barometer of the vast changes this country and the state of California have seen. For almost a century and a half, the U.S. military transformed these grounds into a logistical centerpiece for every American conflict and created a pioneering airfield for early flight experiments. The Presidio served as the headquarters for the Western Defense Command during World War II and until its closure in 1994. The Golden Gate National Recreation Area then embraced a unique opportunity to develop the Presidio into a mixed-use area where it once again became an influential icon as development tackled various social, cultural, and environmental issues to point northern California into a new century while simultaneously tracing this country's past.