Glacial Lake Tonawanda was created with the retreat of the last Wisconsin Glacier. The lake was located east of the Niagara River. It covered the area between most of western New York and Rochester.
Although the lake was large in area, it had shallow water levels. The water along the eastern shore at Rochester, New York was only four feet deep.
At first Lake Tonawanda’s only water outlet was the same as Lake Lundy, at Rome New York. Due to rising land in the east, this outlet was cutoff, forcing waters to seek other outlets.
Lake Tonawanda had a total of five water outlets over the 644 kilometer (400 mile) Niagara Escarpment. These outlets were located in Holley, Medina, Gasport, Lockport and Lewiston, all in New York State.
Only the outlet which became the main spillway was at Queenston – Lewiston. The draining waters flowed over the Niagara Escarpment and this is where the water falls of Niagara were born. This water course continues to be the main outlet which exists today.
Lake Erie was still very large, but the width of the Niagara River was much wider than it is today. The entire area where the Falls are today was under water. The water depth was 9 – 12 meters (30 -40 feet) and the slope, formed by glacial moraine, was on the west edge of Queen Victoria Park. Queen Victoria Park is where both the Skylon Tower and Minolta Tower are now situated. This was a river bank about 12,000 years ago before the gorge was created.
The retreating glacier was the main cause of the reduction in size of the much wider and much deeper glacial river known as the St. David’s River. This transformed the St. David’s River into what is now a smaller and shallower river known as the Niagara River.
As the glacier retreated north, the water flowed to the much lower land which uncovered new land. This caused the draining of the Lake Erie basin and Lake Tonawanda. As these waters drained, the river became much smaller. This resulted in the discovery of land such as Niagara Falls, New York, Grand Island, Three Sisters Islands and Queen Victoria Park in Niagara Falls, Ontario.