Originally named the Bloomington Dam and Lake, the project was renamed in 1987 to honor longtime West Virginia Senator Jennings Randolph, who had a major interest in water resources projects nationwide. The U.S. Army Corps of Engineers built the dam beginning in 1973. It took more than a decade to complete. Water from the lake is drawn into several intakes, depending on the quality and quantity of water available. Another major purpose of the dam is to improve the water quality of the North Branch Potomac.
Water draining into the lake comes from an area with a large number of abandoned coal mines.
Drainage from the mines, which is high in sulfur, creates acidic conditions that are harmful to fish. As the acid water enters the lake, it settles into layers. Reservoir managers can select the best water for release to the North Branch to improve water quality downstream. Water quality improvement in the North Branch has been a major success story in the Upper Potomac in the past decade. Before the dam was built, the North Branch at this point had virtually no aquatic life.