Grand Canyon of Yellowstone
The Grand Canyon of the Yellowstone is the first large canyon on the Yellowstone River downstream from Yellowstone Falls in Yellowstone National Park. The canyon is approximately 24 miles long, between 800 feet (244m) and 1,200 feet (366m) deep and between one quarter of a mile (.45 km) and three quarters of a mile (1.2 km) wide. - wikipedia