Hoover Dam the change, stating, "I didn't know Hoover was that small a man to take credit for something he had nothing to do with." Hoover Dam was recognized as a National Civil Engineering Landmark in 1984. It was listed on the National Register of Historic Places in 1981, and was designated a National Historic Landmark in 1985, cited for its engineering innovations. Other sources Hoover Dam Hoover Dam is a concrete arch-gravity dam in the Black Canyon of the Colorado River, on the border between the U.S. states of Nevada and Arizona. It was constructed between 1931 and 1936 during the
Steamboats of the Colorado River to make only two trips with forty tons in that time. Trips farther up river to the vicinity of Fort Mohave took at least twice as long. The same difficulty plagued the "Colorado" carrying cargo between the estuary and Arizona City. By the fall of 1863 there was a backlog of twelve hundred tons of freight at Arizona City or in ships anchored in the estuary waiting to be brought up river. Between ten and fifty tons of ore waiting to be brought down to the estuary at each of the landings up river above Arizona City. Some of this