Battery Townsley was a casemated battery that mounted two 16-inch caliber guns, each capable of shooting a 2,100 pound, armor-piercing projectile 25 miles out to sea. The guns and their associated ammunition magazines, power rooms, and crew quarters were covered by dozens of feet of concrete and earth to protect them from air and naval attack. This battery, named in honor of Major General Clarence P. Townsley, a general  officer in World War I, was considered the zenith of military technology and was the result of careful, long-term planning. As early as 1915, the army was eager to construct the 16-inch gun batteries at San Francisco, and by 1928, the decision had been made to install two batteries near the city, one on either side of the Golden Gate straits. Three years later, Battery Townsley was completed, and its two guns installed.

Battery Townsley was a high security operation; civilians living in San Francisco knew that there were batteries nearby but their exact locations were not revealed. A battery of this design had never been actually fired before, so the soldiers underwent several months of practice before firing the guns for the first time. The men were subjected to endless training, often under difficult situations: in the rain, in the pitch dark with all the electricity shut off, or with their commanding officer blocking the traditional route to the battery. The practice of dealing with any contingency ensured that the soldiers could operate their guns at a moment’s notice (and almost in their sleep) if ever under enemy attack.  

By summer of 1940, Battery Townsley was ready for testing with live ammunition. The army estimated that the projectile’s farthest range would be 30 miles out to sea, about 5 miles beyond than the Farallon Islands. Waiting for a non-foggy day in July took some patience, but finally, the fog cleared and  the test shot was fired. As the whole mountain shook with the power of this incredible machine, the projectile went even farther than anticipated. Battery Townsley, together with Battery Davis at Fort Funston on the Pacific shore south of the Golden Gate, became the prototypes for the army’s future coastal defenses; the army planned to construct at least 25 additional 16-inch gun batteries along both the nation’s eastern and western seaboards.