Glen Canyon Dam A dam in Glen Canyon was studied as early as 1924, but these plans were initially dropped in favor of the Hoover Dam (completed in 1936) which was located in the Black Canyon. By the 1950s, due to rapid population growth in the seven U.S. and two Mexican states comprising the Colorado River Basin, the Bureau of Reclamation deemed the construction of additional reservoirs necessary. However, the USBR faced opposition when it proposed the Echo Park Dam in Utah's Dinosaur National Monument, which the nascent environmental movement saw as a legal threat to the status of protected lands. After a
Cottonwood Valley (Arizona and Nevada) Cottonwood Valley (Arizona and Nevada) Cottonwood Valley is a wide valley, on the Colorado River on the border between Mohave County, Arizona and Clark County, Nevada. It extends east and west from the river into both states and is the first wide valley south of the Black Canyon of the Colorado, the last in a series of great canyons the Colorado River passes through after leaving the Rocky Mountains on its way west and where it makes its turn to the south toward the Gulf of California. All of the Colorado River in Cottonwood Valley and the lower reach of