Glen Canyon Dam

Construction began in 1956 and took a decade to complete — the result was a 710-foot concrete arch-gravity dam on the Colorado River near Page, Arizona, about 136 miles north of Flagstaff. The dam formed Lake Powell, the second-largest man-made reservoir in the United States, which took more than 17 years to fill. It generates hydroelectric power averaging over 4 billion kilowatt hours annually and remains one of the most contested pieces of infrastructure in the American West. The Carl Hayden Visitor Center offers guided tours.