Originally, Battery Backus housed three six-inch rapid-fire guns. In 1905, those guns were replaced with 4.7-inch guns that were previously mounted at Fort Morgan on Wassaw Island. Battery Gantt was armed with two three-inch rapid-fire guns. These guns, along with the guns from Battery Backus, were to guard the submerged minefield in the river. One officer and twenty-five men were needed to operate this battery.