Glenwood Canyon is a rugged scenic 12.5 mi (20 km) canyon in western Colorado in the United States. Its walls climb as high as 1,300 feet (400 m) 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 routes of Interstate 70 and the Union Pacific's Central Corridor between Denver and Grand Junction.