of use several times in its subsequent history. Between 1866 and 1876, the Corps of Engineers intermittently repaired and modernized Fort Mifflin and upgraded its armament. The army worked on the detached high battery south of the fort from 1870 to 1875 but never finished it. The army built a torpedo (a.k.a. underwater mine) casemate in 1874–1875; its entrance sealed off access to the unused magazine, "Casemate #11", preserving a trove of historical artifacts. These artifacts include pottery, a tin cup, a tin chamber pot, period buttons, and dozens of animal bones. The 1875 Annual Report "The construction of the torpedo casemate has commenced" notes the east magazine torpedo casemate. The army constructed this casemate in 1876. From 1876 to 1884, the Philadelphia District Office of the Corps of Engineers took custodial responsibility of Fort Mifflin. The east magazine (torpedo casemate) first appears on a map in 1886. During World War I the fort was used to store munitions. The army removed the two-story kitchen wings from the officers' quarters building sometime before the 1920s. They were restored in the early 1990s in a major restoration of the building. In 1923 the Marine Barracks held the first recorded USMC Birthday dance. World War II During World War II, the U.S. Army stationed anti-aircraft guns at Fort Mifflin to defend the nearby Fort Mifflin Naval Ammunition Storage Depot (NASD) and the Philadelphia Naval Shipyard. Marine Corps units from the naval shipyard guarded the Naval Ammunition Storage Depot at the northern end of the former Mud and Cabin Islands, and the U.S. Army assigned troops to defend the fort. In April 1942, the U.S. Army stationed Battery H of the 76th Coast Artillery Regiment (Antiaircraft) (Semimobile) (Colored),, the first African-American Coast Artillery unit in U.S. military history, at the fort. On May 24, 1942, the 76th Regiment was relieved and moved to California to prepare for overseas deployment; the U.S. Army then stationed the 601st Coast Artillery Regiment (Antiaircraft) (Semimobile) at Fort Mifflin. Post-war renovations In 1954, Fort Mifflin was decommissioned as an active military post. Several documents reference an old magazine entrance in the location of Casemate #11, and the number 11 comes from a 1954 map associated with the old magazine entrance. Fort Mifflin closed, ranking among the oldest forts in continuous use in the nation's history/ The fort's interior was renovated in 1960. In the 1980s, Harold Finigan, then