The Cumberland Dam was built across the North Branch of the Potomac River at Cumberland, Maryland, for the purpose of diverting water of the river into the head of the Chesapeake and Ohio Canal. The Chesapeake and Ohio Canal Company began construction of its Dam No. 8 in 1837 and work proceeded intermittently, finally concluding in 1850. The dam impounded water over a distance of a mile, causing back water for about 3 miles (4.8 km) up the river. Above the dam is the mouth of Wills Creek.