Hoover Dam 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 Great Depression and was dedicated on September 30, 1935, by President Franklin D. Roosevelt. Its construction was the result of a massive effort involving thousands of workers, and cost over one hundred lives. Originally known as Boulder Dam from 1933, it was officially renamed Hoover Dam, for President Herbert Hoover, by a joint resolution of Congress in 1947. Since about 1900, the Black
Course of the Colorado River the vertical-walled Marble Canyon which is crossed by the twin Navajo Bridges as it enters Grand Canyon National Park. At the southern end of Marble Canyon, the river is joined by another tributary, the capricious Little Colorado River, which drains the Painted Desert region of northeast Arizona and western New Mexico. Although normally a calm and clear spring-fed stream, it can rise dramatically following monsoon storms over the Colorado Plateau. Then the river then turns abruptly west directly across the folds and fault line of the plateau, through the Upper and Lower Granite Gorges of Grand Canyon, which is long