Boulder Canyon (Colorado River) 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 under the eastern end of the Boulder Basin of Lake Mead, between Canyon Point in Nevada and Canyon Ridge in Arizona. Its original mouth is now underneath
Course of the Colorado River into the Salton Sink flooding farmland and creating the Salton Sea, which still exists today as the largest inland body of water in California. The river was finally diverted back to its present course in 1907. Geological evidence suggests that this has happened naturally many times in the past, filling Lake Cahuilla, with the floodwaters slowly evaporating over spans of decades before being re-flooded by the Colorado. The Colorado River meets the Mexico–United States border at the Northern International Boundary (NIB), where the Morelos Dam diverts nearly the entire remaining flow into the Reforma Canal and the Tijuana Aqueduct. Most