Mount Morris Dam was built to protect farm lands, residential areas, and commercial and industrial development in the Genesee River Valley from the dam site north through metropolitan Rochester to Lake Ontario. Before its completion in 1952, a major flood struck the valley about once every seven years. Built at a cost of $25 million, the dam demonstrated its value during Tropical Storm "Agnes" in June 1972, when it prevented an estimated $210 million in flood damage, most of it in the Rochester metropolitan area, even as other parts of the Northeast suffered tremendous destruction. During the storm, water rose to the top of the dam, creating a lake that extended 15 miles upstream through Letchworth State Park.
