Name Image Description Hoover Dam Arch-gravity dam in the Black Canyon of the Colorado River commissioned by the Bureau of Reclamation to control flooding and provide water and hydroelectric power to the Southwestern United States and California.[1] At the time of construction, it was the world's biggest dam and the largest public works project in the history of the U.S.[2][1] Bechtel bid on the project as part of Six Companies, Inc., a group of several smaller contractors.