In 1878, Thomas Edison announced his intention to harness Niagara Falls and produce a safe, electric light system. He said he could do it in six weeks. Almost three years later, all the components -- bulbs, sockets, switches, wires, junction boxes -- were finally ready. The "Wizard of Menlo Park" may have revolutionized the world, but he was caught in a web of personal, patent and corporate battles, eventually losing control of the industry he founded.

Rising more than 700 feet above the raging waters of the Colorado River, it was called one of the greatest engineering works in history. Hoover Dam, built during the Great Depression, drew men desperate for work to a remote and rugged canyon near Las Vegas. There they struggled against heat, choking dust and perilous heights to build a colossus of concrete that brought electricity and water to millions and transformed the American Southwest.