Over thousands of years, natural forces at work in the Potomac Gorge have created a deep, narrow valley. Here, rainwater from 11,500- square mile are up stream is funneled through a constricted passageway, where plants have adapted the ability to survive in the face of intense flood scouring.
The Potomac Gorge is located in the "fall'' zone" where the river passes from the hard, erosion resistant bedrock of the Piedmont to the softer, sandy deposits of the Atlantic Costal Plain. Over this 15-mile corridor, the river drops from an elevation of 140 feet to 10 fet about sea level.
Public parkland in the Gorge inclides the National Park Service;s Chesapeake & Ohio Historical Park and George Washington Memorial Parkway, which administers Turkey Run Park, Great Falls Park, and Glen Echo Park.
The site of the Federal City, at the opening out of the valley where the Potomac breaks over the fall line from Piedmont uplands onto the coastal plain, was chosen for political, practical, and aesthetic reasons. Located on the symbolic dividing line between North and South, and near George Washington’s Mount Vernon estate, the selection placed the city at the head of river navigation, with access to fertile hinterlands and the potential for waterpower from the falls just upriver.
DC listing November 8, 1964