Prince William Forest Park is protected forest in the U.S. state of Virginia within Prince William County (and very partially Stafford County), located adjacent to the Marine Corps Base Quantico near the town of Dumfries. Established as Chopawamsic Recreational Demonstration Area in 1936, the park is the largest protected natural area in the Washington, D.C. metropolitan region at over 16,000 acres (6,500 ha).