We visit Black Canyon this afternoon and my photo from the chasm's south end. Black Canyon is about 12 miles outside of Montrose in Gunnison County, CO.
The Gunnison River drops an average of 43 feet per mile (8 m/km) through the entire canyon, making it one of the steepest river descents in North America. In comparison, the Colorado River through the Grand Canyon drops an average of 7.5 feet per mile (1.4 m/km). The greatest descent of the river occurs in the park at Chasm View dropping 240 feet per mile (45 m/km).
The Black Canyon gets its name on account of its steepness. This steepness makes it difficult for sunlight to penetrate very far down the canyon. As a result, the walls of the canyon are most often draped in shadows, causing the rocky walls to appear black. At its narrowest point the canyon is only 40 feet (12 meters) across at the river.The area was established as a U.S. National Monument on March 2, 1933 and made into a National Park on October 21, 1999.