Black Canyon of the Gunnison National Park comprises of 12 out of the 48 mile-long canyon of the Gunnison River. PinThe South Rim is the most established part of the park with plenty of pullouts and short hikes. 9 THINGS TO DO IN BLACK CANYON OF THE GUNNISON NATIONAL PARK1. Pro Tip: The South Rim has easier hikes and the North Rim has longer and more strenuous hikes. The Gunnison River is the 5th steepest mountain descent river in North America.