Built to harness the tremendous power of the Colorado River, the Hoover Dam is one of the world's most impressive engineering marvels. Rising 726 feet above the border of Arizona and Nevada, the dam attracts thousands of tourists each year. From 1931 to 1935, more than five thousand men worked twenty-four hours a day, seven days a week to successfully complete the dam -- some of them losing their lives. Since its completion, the dam has provided essential...