Lake Tonawanda was a proglacial lake located in what is now western New York State. As the Laurentide glaciation receded the lake existed near the edge of the Niagara Escarpment, east, from its source, the Niagara River, to near the location of the present day community of Holley. The lake had six spillways over the escarpment, at Lewiston, on the Niagara Gorge, Lockport, Gasport, Medina, Shelby, and Holley. At the time Lake Tonawanda existed proglacial Lake Iroquois filled the basin of what is now Lake Ontario.
- Niagara Escarpment field guide, New York Geographic Alliance. Retrieved on 2009-02-22.