Glen Canyon is a natural canyon carved by a 169.6-mile length of the Colorado River, mostly in southeastern and south-central Utah, in the United States. Glen Canyon starts where Narrow Canyon ends, at the confluence of the Colorado River and the Dirty Devil River. A small part of the lower end of Glen Canyon extends into northern Arizona and terminates at Lee's Ferry, near the Vermilion Cliffs. Like the Grand Canyon further downstream, Glen Canyon is part of the immense system of canyons carved by the Colorado River and its tributaries.
In 1963, a reservoir, Lake Powell, was created by the construction of the Glen Canyon Dam, in the Arizona portion of Glen Canyon near Page, inundating much of Glen Canyon under water hundreds of feet in depth. Contrary to popular belief, Lake Powell was not the result of negotiations over the controversial damming of the Green River within Dinosaur National Monument at Echo Park; the Echo Park Dam proposal was abandoned due to nationwide citizen pressure on Congress to do so. The Glen Canyon Dam remains a central issue for modern environmentalist movements.