Hoover Dam, in Blendon Township, Franklin County, Ohio, near Westerville, dams Big Walnut Creek to form the Hoover Memorial Reservoir. Construction began during 1953 due to the increased water demand of post-war Columbus. The project was completed and dedicated in 1955 and the dam officially opened in 1958. It was named for two brothers, Charles P. Hoover and Clarence B. Hoover, to honor their careers with the City of Columbus Waterworks.
The dam's reservoir is a major water source for the city of Columbus. It holds of water and has a surface area of , or about five square miles. The dam is 2,583 ft (787 m) long, including 680 ft (210 m) of spillway. It was constructed from 180,000 ft<sup>3</sup> of concrete (5,100 m<sup>3</sup>) and 591,500 ft<sup>3</sup> of earth (16,750m<sup>3</sup>).
The dam reaches a maximum height of 94 ft (29 m) above the stream bed, and is 911 ft (278m) above sea level at its peak elevation. The uncontrolled spillway reaches a peak elevation of 890 ft (270 m) above sea level.