Lake Powell, on the border of Arizona and Utah, was created by the construction of Glen Canyon Dam along the Colorado River. The dam, which was completed in 1963, is 710 feet high and didn't fill up until 17 years after it was completed.
When the region needed to solve a long-running water dispute, Glen Canyon Dam was chosen by the U.S. government after David Brower of the Sierra Club suggested it was a better location than the government's choice of Echo Park, Colo. Unfortunately, Brower made the suggestion before actually seeing Glen Canyon. Despite efforts to overturn the decision, the dam was constructed and miles of canyons, streams, and archeological and wildlife habitat were swallowed up by the waters.
Today, Lake Powell is a recreational area — and ironically, low lake levels are hurting tourism. One of the small bright spots in a bad situation is that some of the previously submerged sites are seeing the light of day again. (It's too bad it took an ecological crisis to return the land to its natural state, even temporarily.)