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 and launched. Steamboats of the Colorado River Steamboats on the Colorado River operated from the river mouth at the Colorado River Delta on the Gulf of California in Mexico, up to the Virgin River on the Lower Colorado River Valley in the Southwestern United States from 1852 until 1909, when the construction of the Laguna Dam was completed. The shallow draft paddle steamers were found to be the most economical way to ship goods between the Pacific Ocean ports and settlements and mines along the lower river, putting in at landings in Sonora state, Baja California Territory, California state, Arizona