The reservoir first impounded the water of Old Mill Stream and Red Clay Creek in 1932, with a dam built by the city of Wilmington, Delaware, for municipal drinking water.

It has a water surface of 187 acres (76 ha), a maximum capacity of 11,000 acre-feet (14,000,000 m3), and a normal capacity of 6,300 acre-feet (7,800,000 m3).

[1] The reservoir and its surroundings have been open to the public since 1971.

The dam, Edgar M. Hoopes Dam (National ID # DE00015), is a concrete gravity dam originally built in 1932 and restructured several times since.

[1] Its namesake, Edgar M. Hoopes, was Chief Engineer of the Wilmington Water Department from 1913 through 1918, according to a plaque on site.