But most people measure the canyon in river miles, along the course of the Colorado River at the bottom of the canyon. By that standard, Grand Canyon is 277 miles / 446 km long. It begins at Lees Ferry (mile 0) and ends at the Grand Wash Cliffs (mile 277 / km 446). The Colorado River is longer, of course: 1450 miles / 2333 km long from the Rocky Mountains of Colorado to the Gulf of California in Mexico. Grand Canyon is only one of many beautiful canyons which the river has carved. Others include Cataract Canyon and Glen Canyon - the latter now beneath the waters of Lake Powell.