George Washington Memorial Parkway
Annual visitors: 7.3 million
Location: Washington, D.C., and Alexandria, Va.
Size: 25 miles
Founded: 1930
Highlights: The parkland surrounding the Parkway offers visitors a chance to explore nature or to learn about history. The 485-acre Dyke Marsh, for example, is one of the largest tidal wetlands in the region, while the U.S. Marine Corps Memorial features a statue of the iconic photo of the second flag raising at Iwo Jima.
