As war clouds gathered in the late 1930s, the Army started building massive fortifications at the entrance to the Delaware River and Bay. Called Fort Miles, the main batteries and headquarters were at Cape Henlopen, Delaware, near the main shipping channel, while a supporting battery and lookout towers were located on the Cape May side of the Bay.
Fort Miles' charge was the protection of the highly strategic industrial centers along this waterway, including the DuPont munitions and chemical plants in Wilmington, oil refineries in Chester and shipyards in Philadelphia and Camden. Following a nationwide Harbor Defense Modernization plan, the Army Corps of Engineers began pouring the eleven-foot thick concrete emplacements for a pair of 16-inch guns in 1940. These guns (similar to those on the Battleship New Jersey) were to be the primary weapons of the fortification. The plan also called for the five additional batteries, including a 12-inch battery, two 6-inch support batteries and a 6-inch battery on the Cape May side. Together, these guns sealed off our region from enemy invasion. In addition to the land-based protection, Fort Miles also had minefields, patrol boats and airplanes to protect the Delaware River and Bay.