[3] The fort was completed just before the American Civil War by the United States Army, to defend San Francisco Bay against hostile warships.

[5] Mexico won independence from Spain in 1821, gaining control of the region and the fort, but in 1835 the Mexican army moved to Sonoma leaving the castillo's adobe walls to crumble in the wind and rain.

On July 1, 1846, after the Mexican–American War broke out between Mexico and the United States, U.S. forces, including Captain John Charles Fremont, Kit Carson and a band of 10 followers, captured and occupied the empty castillo and spiked (disabled) the cannons.

The gold rush of 1849 had caused rapid settlement of the area, which was recognized as commercially and strategically valuable to the United States.

In 1854 Inspector General Joseph K. Mansfield declared "this point as the key to the whole Pacific Coast...and it should receive untiring exertions".

Colonel Albert Sidney Johnston, commander of the Department of the Pacific, prepared Bay Area defenses and ordered in the first troops to the fort.

The Confederate raider CSS Shenandoah planned to attack San Francisco, but on the way to the harbor the captain learned that the war was over; it was August 1865, months after General Lee surrendered.

Soldiers from the 6th U.S. Coast Artillery were stationed there during World War II to guard minefields and the anti-submarine net that spanned the Golden Gate.

On October 16, 1970, President Richard Nixon signed a bill creating Fort Point National Historic Site.

[8] Fort Point is designated as California Historical Landmark #82, officially listed under the site's original name, Castillo De San Joaquín.