Fort Dupont was erected as part of the Eastern Branch Line Defenses (Anacostia River). Constructiobn commenced between Ocotober and December of 1861, and "completed" in the spring of 1862. The fort was built to protect a critical Ridge
Road (Alabama Avenue) intersection and was supported by Forts Meigs and Chaplin to the north and Fort Davis to the south.

Fort DuPont was a regular hexagonal redoubt, designed for 14 guns, 12
firing through embrasures. Fort Dupont had six sides, each 100 feet long, protected by a deep moat and trees felled side-by-side with branches pointing outward. It was named for Flag Officer Samuel F. Dupont, who commanded the naval victory at Port Royal, South Carolina, in November 1861.

It was never a strong work and in 1862, a commission studying the Defenses of Washington noted that a deep ravine to the west of the fort should be covered by a blockhouse. At other times, traverses to cover the sally port, magazine and rifle pits to the cover approaches were recommended.

In April 1864, Brigadier General John G. Barnard, Chief Engineer, advised the abandonment of Fort Dupont. The army officially abandoned the fort in 1865. The grounds reverted to its original landowner, Michael Caton. 

Although its garrison and guns never saw battle, Fort Dupont served as a lifeline of freedom. Runaway slaves found safety here before moving on to join the growing community of "contrabands" in Washington. The barracks and guns are gone, but the fort's earthworks can still be traced near the picnic area on Alabama Avenue.

In the 1930s, the National Capital Planning Commission acquired the old fort and surrounding land for recreation. A golf course was constructed and as the city grew, golf gave way in 1970 to the sports complex along Ely Place that now includes tennis and basketball courts, athletic fields, a softball diamond, and an indoor ice rink.  Once where soldiers viewed farmlands, park visitors now grow fruits and vegetables in the community garden.