The Dismal Swamp Canal, the oldest operating canal in the country, is a 22-mile-long manmade waterway that runs north to south through the Great Dismal Swamp. Lake Drummond, one of only two natural lakes in Virginia, is located approximately in the center of the swamp. A series of locks controls the water level in the canal and the release of water from the lake. The Dismal Swamp Canal is one of two alternate routes along the Atlantic Intracoastal Waterway. The construction of the canal, authorized by the Virginia legislature in 1787 and ratified by North Carolina in 1790, began at both ends in 1793 and was completed in 1805. The canal was the key transportation artery and inland link between southeast Virginia and northeast North Carolina. The feeder ditch from Lake Drummond was cut in 1812, and three of four locks were constructed. Between 1827 and 1829 the canal was widened and deepened. The canal suffered severe damage during the Civil War, as it was heavily used by occupying Union forces. During the late 1890s substantial improvements were made to the waterway. In 1929 the U.S. Army Corps of Engineers took over the operation.