Built by Union forces to defend the nation's capital against Confederate troops, the Civil War Defenses formed a 37-mile ring around the city of Washington. The Army began construction of the fortifications in the early 1860s along the ridges that rise up from the lower river terraces of the Potomac and Anacostia Rivers. By 1865, the defenses included 68 forts, supported by twenty miles of rifle pits and covered ways, with 32 miles of military roads. Constructed mostly of sod, earth and timber, the fortification system defended the city well, especially during the Battle of Fort Stevens, where President Abraham Lincoln was present.
Abandoned after the war, the network of green, open spaces and hilltop views became a catalyst for one of the first urban planning efforts for public recreation. The McMillan Plan of 1902 recommended transforming over 350 acres into the system of Fort Circle Parks, adding much-needed park space to the city. Efforts have continued since then to realize the McMillan Plan vision, with varying success. Among other projects, the Civilian Conservation Corps created roads and facilities at Fort Dupont, and M. Paul Friedberg designed a playground at Fort Lincoln that utilized the 100-year-old earthworks on the site. Today, nineteen of the fort sites are administered by the National Park Service, while four are administered by other jurisdictions.