In the 1940s and early 1950s, the U.S. Bureau of Reclamation planned to construct a series of Colorado River dams in the rugged Colorado Plateau province of Colorado, Utah and Arizona. Glen Canyon Dam was born of a controversial dam site the Bureau selected in Echo Park, in what is now Dinosaur National Monument in Colorado. A small but politically effective group of objectors led by David Brower of the Sierra Club succeeded in defeating the Bureau's bid, citing Echo Park's natural and scenic qualities as too valuable to submerge.

But by agreeing to a relocated dam site near Lee's Ferry, between Glen and Grand Canyons, Brower did not realize what he had gambled away. At the time, Brower had not actually been to Glen Canyon. When he later saw Glen Canyon on a river trip, Brower discovered that it had the kind of scenic, cultural, and wilderness qualities often associated with America's national parks. Over 80 side canyons in the colorful Navajo Sandstone contained clear streams, abundant wildlife, arches, natural bridges, and thousands of Native American archeological sites. By then, however, it was too late to stop the Bureau and its commissioner Floyd Dominy from building Glen Canyon Dam. Dominy was a firm believer in putting the river to human use, once saying "Now I admit that nature can't improve upon man. We're probably the supreme being." Brower believed the river should remain free, and would forever after consider the loss of Glen Canyon his life's ultimate disappointment.

Construction on Glen Canyon Dam began with a demolition blast keyed by the push of a button by President Dwight D. Eisenhower at his desk in the Oval Office on October 1, 1956. The first blast started clearing tunnels for water diversion. On February 11, 1959, water was diverted through the tunnels so dam construction could begin. Later that year, the bridge was completed, allowing trucks to deliver equipment and materials for the dam, and also for the new town of Page, Arizona.

Concrete placement started around the clock on June 17, 1960. The last bucket of concrete was poured on September 13, 1963. Over 5 million cubic yards (4,000,000 m³) of concrete make up Glen Canyon Dam. The Dam is 710 feet (216 m) high, with the surface elevation of the water at full pool being approximately 3700 feet (1100 m).

Construction of the Dam cost $155 million, and 18 lives were lost in the process. From 1963 to 1966, turbines and generators were installed for hydroelectricity. On September 22, 1966, Glen Canyon Dam was dedicated by Lady Bird Johnson.

Upon completion of Glen Canyon Dam on September 13, 1963, the Colorado River began to back up, no longer being diverted through the tunnels. The newly flooded Glen Canyon formed Lake Powell.

It took 17 years for the lake to rise to the high water mark, on June 22, 1980. Since then the lake level has fluctuated considerably depending on the seasonal snow runoff from the mountains.