The seacoast defenses for San Francisco Bay span more than 200 years of history, and were constructed by three different nations. These fortifications constitute one of the best and most extensive museums of military architecture in North America. Only those of New York Harbor exceeded them in strength and number. The San Francisco Bay fortifications are further discussed under the following periods. Click on the representative photos to learn more about a time period.

	Spanish and Mexican period from 1776 to 1846 These fortifications include El Presidio, Castillo de San Joaquin, and Bateria San Jose. Unfortunately, little remains of these structures except for six brass cannon and some foundations of El Presidio.
	American "Third System" period from 1850 to 1884 These fortifications include Fort Point, Alcatraz Island, Camp Reynolds, Fort Mason, and older batteries bordering the Golden Gate.
	Harbor Defenses of San Francisco from 1891 to 1948 These fortifications include those constructed during the Endicott, Taft, and World Wars I and II periods. Their locations are at Fort Baker, Fort Barry, Fort Cronkhite, Fort Funston, Fort Mason, Fort Miley, Fort Scott, Fort McDowell, Milagra Ridge, and Crissy Field.
	Cold War Era from 1952 to 1974 Nike Missile sites were located at Fort Baker, Fort Barry, Fort Cronkhite, Fort McDowell, the Presidio and other sites around the bay. Nike site SF-88L at Fort Barry has been thoroughly restored as a museum and is widely recognized as the nation's finest example of this weapon system.

Glossary of Military Terms