The Presidio One and one-half the size of Central Park in New York, this national treasure is 1400 acres and represents 45% of San Francisco's open space. The Presidio has roughly 900 buildings, of which about 500 are considered to be historic. This frontier military fortification, established in 1776, guarded the land against foreign incursions and protected neighboring missions from hostile Indians. Many exciting developments have included new findings of original foundations.