View down Glenwood Canyon at Hanging Lake Rest Area. Interstate 70 passes through tunnels along this section of the canyon. The Leadville Formation is visible in the upper left.
Glenwood Canyon is a rugged scenic 12.5 mile (21 km) gorge on the Colorado River in western Colorado in the United States. Its canyon walls climb as high as 1300 (400m) feet above the Colorado River. It is the largest such canyon on the Upper Colorado. The canyon, which has historically provided the routes of railroads and highways through western Colorado, currently furnishes the route of Interstate 70 between Denver and Grand Junction. The canyon stretches from near Dotsero, where the Colorado receives the Eagle River, downstream to the WSW to just east of Glenwood Springs, on the mouth of the Roaring Fork. Most of the canyon is in Garfield County, with the upper portion near Dotsero lying in Eagle County.
In 1906, the canyon provided the route of the Taylor State Road, a gravel road that was the first route for automobiles through the Colorado Rockies. The canyon also provided the route for the Denver and Rio Grande Western Railroad in the early 20th century. Through acquisitions, the line is currently part of the Union Pacific system. A monument to the dome car design was originally installed in this canyon but removed to make way for the construction of Interstate 70.1 The monument is now on display at the Colorado Railroad Museum in Golden.2
The canyon is widely considered one of the most scenic natural features on the Interstate Highway System of the United States. Foot access to the canyon is available at four rest areas along Interstate 70 in the canyon. The Hanging Lake Rest Area (Exit 125) provides access to the canyon along a stretch where I-70 is concealed in tunnels.
The canyon was formed relatively recently in Pleistocene time by the rapid cutting of the Colorado down through layers of sedimentary rock. The upper layers of the canyon are sandstone from Pennsylvanian and Mississippian. Sections of the lower canyon walls are made of Cambrian rock. The Mississippian layer that is prominent throughout much of the upper rim sections of the canyon is part of the Leadville Formation.
