Black Canyon of the Gunnison National Park is a United States National Park located in western Colorado and managed by the National Park Service. There are three entrances to the park. The more-developed east entrance is located 37 miles (59 km) east of Montrose and just west of Blue Mesa Reservoir by Blue Mesa Point. The south rim entrance is located 15 miles (24 km) east of Montrose, while the north rim entrance is 11 miles (18 km) south of Crawford and is closed in the winter. The park contains 12 miles (19 km) of the 48-mile (77 km) long canyon of the Gunnison river. The national park itself contains the deepest and most dramatic section of the canyon, but the canyon continues upstream into Curecanti National Recreation Area and downstream into Gunnison Gorge National Conservation Area.

The Gunnison River drops an average of 34 feet per mile (5 m/km) through the entire canyon, making it the 5th steepest mountain descent in North America. By comparison, the Colorado River drops an average of 7.5 feet per mile (1.4 m/km) through the Grand Canyon. The greatest descent of the Gunnison River occurs within the park at Chasm View dropping 240 feet per mile (45 m/km). The Black Canyon is so named due its steepness which makes it difficult for sunlight to penetrate into its depths. As a result, the canyon is often shrouded in shadow, causing the rocky walls to appear black. At its narrowest point the canyon is only 40 feet (12 m) wide at the river.

The extreme steepness and depth of the Black Canyon formed as the result of several geologic processes acting together. The Gunnison River is primarily responsible for carving the canyon, though several other geologic events had to occur in order to form the canyon as it is seen today.

en.wikipedia.org/wiki/Black_Canyon_Of_The_Gunnison