It was originally called keenhongsheconsepung, a Delaware word literally translated as "sharp tool river", based on the shale found along its shores.

In 1833, the Ohio General Assembly passed legislation intending to restore the original Native American names to some Ohio waterways, but mistakenly gave Whetstone River the name "Olentangy"—Delaware for "river of the red face paint"—which had actually belonged to what is now known as Big Darby Creek.

The river continues southward towards the communities of Delaware, Powell, Worthington, and the village of Riverlea, before reaching Columbus, beginning with Clintonville and flowing through Old North Columbus, the campus of The Ohio State University, and the historic complex of neighborhoods to the south before merging with the Scioto River in the Arena District at location known as Confluence Park.

The reservoir is located 5 miles north of the city of Delaware, and was built by the U.S. Army Corps of Engineers for flood control purposes.

The water level came within less than 1 foot of the top of the dam, requiring the main spill gates to be opened before it began dropping.