Designed as part of the massive modernization program of U.S. seacoast fortifications initiated by the Endicott Board, construction on Fort Casey began in 1897. In 1901, her big guns on disappearing carriages, which could be raised out of their protective emplacements so that the guns were exposed only long enough to fire, became active. However, the fort's ammunition batteries became obsolete almost as soon as their construction was completed. The invention of the airplane in 1903, and the subsequent development of military aircraft made the fort vulnerable to air attack. In addition, the development of battleships designed with increasingly accurate weaponry transformed the static strategies of the nineteenth century into the more mobile attack systems of the twentieth century. Most of Fort Casey's guns and mortars were removed and sent to Europe and the Pacific during World War I, where they were mounted on railcars to serve as mobile heavy artillery.
In 1935, the Coast Artillery withdrew the station's battery assignments and placed it on inactive status. As World War II approached, military officials reactivated Fort Casey after making physical improvements to the aging frame-plaster construction.
Two of the fort's 10-inch (25-cm) seacoast artillery guns on their carriages were salvaged in the mid-1960s from their final active duty location at Fort Wint on the U. S. Naval Base Subic Bay. The guns showed visible shrapnel scarring from the effects of the Japanese bombings in the Philippines at the opening of World War II. Two 3-inch (76-mm) rapid-fire guns from Fort Wint are also mounted at Fort Casey.