National Mall and Memorial Parks: Old Post Office Tower
900 Ohio Drive, SW
Washington, DC 20024
Phone: 202-606-8691
202-606-8694
Did You Know?
The Great Falls of the Potomac River is the second largest in the state of Maryland. It is a series of cascading falls. Water drops 76 feet in two-thirds of a mile. Natural hazards in the Potomac such as water falls and rapids created the need for canals for reliable water transportation.