system of national monuments and government-owned parks and recreation areas in and around the District of Columbia, U.S. The system was authorized by the U.S. Congress in 1790 and became part of the National Park Service in 1933.

Today there are more than 300 park units with a combined area of 10 square miles (26 square km). The overwhelming majority of units are located in Washington, D.C.; others are in Virginia and Maryland. Units include the Washington Monument, the Jefferson Memorial, the White House, the Lincoln Memorial, the Vietnam Veteran's Memorial, the President's Parks, and the Frederick Douglass Home, all in Washington, D.C., as well as Prince William Forest Park and the Arlington House (Custis-Lee Mansion) in Virginia.