Lake Tonawanda was a prehistoric lake that existed approximately 10,000 years ago at the end of the last ice age, in Western New York, United States. The lake existed on the southern (upper) side of the Niagara Escarpment east of the present course of the Niagara River between Early Lake Erie to the south and Glacial Lake Iroquois (the ancestor of Lake Ontario) to the north. During the retreat of the glaciers, the water levels of the Great Lakes were higher. Lake Tonawanda was created and fed by the elevated waters of Lake Erie. Lake Tonawanda itself was drained into Lake Ontario by a series of falls over the escarpment, including one at present day Lockport, New York.