River, Pennsylvania and New York, U.S. It flows north from its headwaters in Pennsylvania, bisecting Rochester , N.Y., to enter Lake Ontario after a course of 158 mi (254 km).
Midway along its course, it flows into a 25-mi (40-km) gorge with sides rising at times 800 ft (245 m) above its banks. Called the "Grand Canyon of the East," it is the focal point of Letchworth State Park.