National Geographic : 1946 Jan
Nevada, Desert Treasure House U. S. Bureau of Reclamation Boulder Dam Tamed and Harnessed the Mad, Galloping Colorado River Wedged between Nevada and Arizona in precipitous Black Canyon, this 726-foot-high block of concrete stemmed river floods and created Lake Mead, 115 miles long. Dwarfed by the dam is the power plant below. It is two city blocks long and has an ultimate capacity of 1,322,300 kilowatts. Dark specks on the rim are cars.