The fort had a typical armament for its day, with a few exceptions. The main armament was Battery Arnold (3 12-inch guns) and Battery Harker (3 10-inch guns). These were on disappearing carriages to allow the guns to normally remain hidden from observation from the river. Flanking these were Battery Gregg, with two 5-inch M1900 guns on M1903 pedestal mounts, and Battery Krayenbuhl, with two 5-inch M1897 guns on balanced pillar mounts, each with all-around fire. Battery Krayenbuhl was sited atop the fort's smallest and most unusual battery, Battery Edwards with two 3-inch mine defense guns in large casemates rebuilt from earlier (1872) magazines. These casemated light guns, intended to protect an underwater minefield in the river by driving off minesweepers, were a unique installation in US forts of this era, in which virtually all emplacements were open-top.