Boulder Canyon (Colorado River) steamboats as they passed over the dangerous rapids of Devil's Gate Canyon, during their high water runs to the mouth of the Virgin River at Rioville, Nevada. Boulder Canyon (Colorado River) Boulder Canyon, originally Devils Gate Canyon, is a canyon on the Colorado River, above Hoover Dam, now flooded by Lake Mead. It lies between Clark County, Nevada and Mohave County, Arizona. It heads at western end of the Virgin River Basin of Lake Mead, at about . Boulder Canyon divides the Black Mountains into the Black Mountains of Arizona, and the Black Mountains of Nevada. Its mouth is now
Steamboats of the Colorado River the Colorado Steam Navigation Company between Yuma and Needles. By the end of 1905 all the steamboats, "Cochan", "St. Vallier" and "Searchlight", were withdrawn down river to Yuma. Their places were taken by smaller gasoline powered boats, until they were in turn replaced by trucks. The remaining steamboats worked on irrigation projects on the lower part of the river and on repairing the 1904-1907 breach in the Alamo Canal, that directed the Colorado River into the Salton Sink and created the Salton Sea before it was repaired. The last project, the construction of the Laguna Dam ended steam navigation on