Dyke Marsh is a freshwater tidal wetland and wildlife preserve along the Potomac River between Alexandria and Mount Vernon, managed as part of the George Washington Memorial Parkway. Formed roughly 5,000 to 7,000 years ago where upriver fresh water meets saltier tidal water, it now contains about 380 acres of marsh, floodplain, and swamp forest within 485 acres, making it one of the Baltimore-Washington region’s largest remaining freshwater tidal wetlands. Nearly 300 bird species and more than 360 plant species have been recorded there, though dredging in the 1950s and 1960s greatly reduced its size. Today it remains both an ecological refuge and a popular destination for birdwatchers and other visitors.

Fort Washington, Maryland · USA