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
Agriculture in the Southwestern United States Agriculture in the Southwestern United States Agriculture in the Southwest United States is very important economically in that region. The three main watersheds of the southwest United States are the Colorado River Basin, the Great Basin, and the Rio Grande Basin. The Colorado River Basin includes parts of California, Utah, Arizona, New Mexico, Colorado, and Wyoming. The Colorado River is the largest river in the Southwest United States. The Great Basin watershed includes parts of southern California, most of Utah, the northwest half of Nevada, and parts of Oregon and Idaho. The Rio Grande Basin includes most of New Mexico,