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
Glen Canyon Dam Bridge Glen Canyon Dam Bridge The Glen Canyon Bridge or Glen Canyon Dam Bridge is a steel arch bridge in Coconino County, Arizona, carrying U.S. Route 89 across the Colorado River. The bridge was originally built by the United States Bureau of Reclamation to facilitate transportation of materials for the Glen Canyon Dam, which lies adjacent to the bridge just upstream. The two-lane bridge has an overall length of with a deck above the river, making it the one of the highest bridges in the United States. The bridge was the highest arch bridge in the world when completed in 1959.