The National Capital Parks was a unit of the National Park System of the United States, now divided into multiple administrative units. It encompasses a variety of federally owned properties in and around the District of Columbia including memorials, monuments, parks, interiors of traffic circles and squares, triangles formed by irregular intersections, and other open spaces.

The Civil War Defenses of Washington were a group of Union Army fortifications that protected the federal capital city, Washington, D.C., from invasion by the Confederate States Army during the American Civil War.