Hoover Dam on the Colorado River, is a feature of the Boulder Canyon Project. Located on the Arizona-Nevada state line, at 726 feet it is the highest concrete dam in the United States, a National Historic Landmark, and one of America's Seven Modern Civil Engineering Wonders. The Bureau of Reclamation started conducting guided tours through Hoover Dam and Powerplant in 1937. More than 1,000,000 visitors
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