Art Deco wonder of the west, which created the largest man-made lake in the country, Lake Mead. It was built primarily to control flooding and provide a stable supply of water downstream, secondarily to produce electricity, and tertiarily to employ people, and to prove that it could be done. Completed in 1935, it is still the highest concrete dam in the Western Hemisphere. The Hoover Dam and the reservoir it formed can hold back two years of the flow of the Colorado River, changing the river, in the words of a Bureau of Reclamation brochure, "from a natural menace to a national resource."