The Delaware Bay has long been a vital location for the United States for its access to the Delaware River, and has been defended and fought over since colonial times. But before World War I, the Delaware River’s fortifications were obsolete and the Bay’s coastal defenses were lacking, despite the important Philadelphia Naval Shipyard and key manufacturing and refining operations in the region.

The start of World War I saw the development of a naval base at Cape Henlopen to support coastal vessels, such as sub chasers and minesweepers to defend against German U-Boats attacks along the approaches to Delaware Bay. Emergency 6-inch gun batteries were installed at both Cape May, NJ and at Cape Henlopen in case unauthorized shipping tried to enter the bay. These defenses were withdrawn after the end of World War I.

Permanent coast artillery in the form of four 12-inch long-range guns were installed at Delaware’s Fort Saulsbury by the end of World War I, but the fort was soon placed on caretaker status. The 1920s and start of the Great Depression resulted in little government funding for new defenses for Delaware Bay.

During the 1930s, the rise of overseas naval threats resulted in plans for new defenses at the entrance to the Bay from both the U.S. Army and the U.S. Navy. Temporary defenses were put in place in 1938 when mobile coast artillery in the form of 8-inch railway guns and 12-inch railway mortars came to Cape Henlopen to practice. Construction of permanent defenses resulted in naval and aviation bases at Cape May, an army fort at Cape Henlopen, and an army airfield at Dover. Fort Miles, built between 1941 and 1944, was located at Cape Henlopen, along with a sub-post at Cape May.

It was a new use for Cape Henlopen, which had been used as a quarantine station, lighthouse location, naval radio station, naval base, and for temporary gun emplacement – but never the site of a key harbor defense installation.

After Nazi Germany invaded Western Europe in 1940, U.S. defense planners intensified their efforts to build Delaware Bay’s coastal fortifications. In 1941, construction of two artillery batteries, Battery Smith (2-16-inch BC) and Battery 22 (4-155mm mobile) were begun, with Battery #519 (2-12-inches BC), Battery Herring (2-6-inches SBC), and Battery Hunter (2-6-inches SBC) undertaken in 1942. Eventually, Fort Miles would house nearly 2,500 soldiers and civilian personnel, cover more than 1,000 acres, and cost $22 million to build – worth $420 million in today’s dollars.

The mouth of the Delaware Bay by the end of World War II was defended by 12 batteries of U.S. Army coast artillery between Fort Miles and Cape May, NJ. These included anti-aircraft and anti-motor torpedo boat guns (3-inches and 90 millimeters), secondary guns (155 millimeters and 6-inches), railway guns (8-inches), and primary guns (12-inches and 16-inches).

Fifteen concrete fire control towers were built, 11 along the Delaware’s Atlantic coastline and 4 across Delaware Bay in New Jersey. These towers were manned to sight and track enemy warships. Additionally, five steel fire control towers were built along Delaware Bay itself. In 1941, a controlled submarine mine complex was built at Fort Miles to support three lines of mines across the Bay’s primary shipping channel. These mines were organized into 35 grand groups, each having 13 M4 ground mines by the end of the war.

While German U-Boats laid mines (which resulted in the sinking of the tug John R. Williams off the entrance of the bay’s Harbor of Refuge in June 1942 with the loss of 14 seaman out of its crew of 18) and torpedoed several ships off the coast of Delaware during the war, no enemy warships threatened Fort Miles during World War II.

Fort Miles entered a transition period away from its coast artillery role as in the late 1940s and 1950s. In March 1946 the harbor defenses of the Delaware Bay were inactivated and a small Army detachment remained as caretakers. The Army undertook the scrapping of the coast defenses at Fort Miles in 1948 and by 1949 its remaining harbor defenses responsibilities were transferred to the Navy. By 1950, the entire U.S. Coast Artillery Corp was disbanded as no foreign naval threats against the US were identified given the outcome of World War II and a strong desired by the government to reduce overall military fiscal expenditures.

While the Army used Fort Miles primarily for the storage of ammunition, the Navy used the fort for their expanded harbor defense role through the use of controlled submarine mines and underwater detection systems, which then located in the former Battery Hunter. The Navy also established an early anti-aircraft missile testing station at Herring Point as part of Operation Bumblebee.

The Korean War and the beginning of the Cold War saw the rise in military spending and the use of Fort Miles by the Army, especially for anti-aircraft artillery training and for overflow housing of soldiers. One of the primary Army functions at Fort Miles was for moral, welfare, and recreation (MWR) activities as part of the First Army Recreation Area. The US Navy also begun to use Cape Henlopen more for their missions, so the Army transferred 593 acres of Fort Miles to the Navy in 1956. In an effort to save money the Army decided to close Fort Miles in 1958.

As the Cold War deepened, former Fort Miles gain several new missions relating to homeland defense. The Army installed a Gap Filler Radar Station on FC Tower #12 which was then relocated to the former Battery #519. This radar station was part of the continental air defenses system (Nike Air-to-Ground Missiles). The Army continued to use the former Fort Miles for training, such as Operation Wet Horse II, an amphibious assault exercise designed to test the capability of reserve units to conduct large-scale landing operations which took place in May 1962.

The Navy built a Sound Surveillance System (SOSUS) facility in 1961-62 on the southern end for the former Fort Miles reservation using both the former Batteries Smith and Herring as well as several new buildings (NAVFAC Lewes). The SOSUS system consisted of bottom-mounted hydrophone arrays connected by underwater cables to a processing facility ashore. This allowed for the detection and tracking of Soviet submarines by their faint acoustic signals.

The Navy also installed a Naval Radio Station in the former Battery Hunter, but due to the need for more space to support the tropospheric scatter system and related equipment the station was moved to the former Battery 519, where several microwave antennas were installed the former battery’s roof.

The Army offered to transfer 554 acres to the State of Delaware for recreation purposes and in October 1964 the State formally accepted this former Fort Miles property as the Cape Henlopen State Park. Many of Army’s abandoned buildings are removed in the coming years to reduce the State’s cost of maintenance.

The development of satellite communications capabilities annulled the Navy’s requirements for troposcatter communications so in 1970 both the radio stations and naval ships supporting this system were decommissioned, including the radio station in the former Battery 519 and the station’s antennae were removed at Cape Henlopen.

The SOSUS Naval Facility Lewes closed in September 1981 and the Naval Reserve Training Facility Lewes was established in its place. In 1980 consolidation and elimination of expensive individual SOSUS facilities was made possible by the Wideband Acoustic Data Relay (WADR) so that SOSUS arrays could be remoted directly to the Naval Ocean Processing Facility (NOPF) at Dam Neck, Virginia allowing the closure of NAVFAC Lewes.

The newly established NAVRESFAC Lewes headquarters occupied the former NAVFAC Lewes multi-purpose building (now the Biden Center) which allowed several Delaware naval reserve units to conduct training activities at Cape Henlopen. The largest naval reserve unit, MIUW moved from the former Battery Hunter to the former NAFAC Auxiliary Building (the former Battery Smith). This consolidation allowed the Navy to transfer more land to the Cape Henlopen State Park in 1983, so the Navy’s land holdings was reduced to about 17 acres around these structures.

More military controlled land was transferred to the state park when the Army ceased operation its MWR facility at Cape Henlopen altogether in 1991, as part of the Base Realignment and Closure Commission (BRAC) process. This area, consisting of approximately 96 acres around the beach and the cantonment area of the former Battery 519, was transferred to the State of Delaware.

In 1995, it was announced that Senator Biden was seeking the transfer of the land on which the Naval Reserve Facility was located for inclusion in the Cape Henlopen State Park. Despite a continuing need for the training facility, the Navy could no longer justify keep the facility open. So, in 1996, after almost 100 years at Cape Henlopen, the final military units left and the Navy transferred the remaining land to the State of Delaware. The Navy’s multi-purpose structure was repurposed into the Biden Environmental Training Center for overnight conferences on environmental issues and park offices.

In the late 1990s awareness in the military history of Cape Henlopen grew, especially under the direction of Leland G. Jennings, Jr., who was the Chief Historian and Director of Cultural Affairs for the Delaware State Parks. This interest in preserving and interpreting the former Fort Miles resulting in the formation of the Fort Miles Historical Association (FMHA) in 2003, spearheaded by Gary Wray and Lee Jennings. Since 2004, batteries, barracks and numerous other structures original to former Fort Miles have been preserved and restored by the combined efforts of Fort Miles Historical Association and Delaware State Parks. As a result, Fort Miles Museum now comprises of exhibits depicting its history both inside the former Battery 519 and outside in the Artillery Park/Cantonment Area.