Watch soap2day. In the first half of the 20th century, America's railroads were radically transformed by the innovation of gargantuan steam locomotives. Pushed by the need to haul ever longer and heavier trains, the nation's locomotive works responded with the invention of awe-inspiring articulated engines. Delivering up to 7,500 horsepower, these steel behemoths could haul mile-long, 15,000-ton trains. In this riveting program, journey back to the golden age of steam for an up-close look at these legendary locomotives. See the Union Pacific's famed "Big Boy" in action and ride the rails of the Chesapeake & Ohio and Norfolk & Western railways. Meet the men who drove engines like the Allegheny and Yellowstone, and visit the museums and yards where the largest steamers ever built remain preserved in time. THE HISTORY CHANNEL' proudly presents this rollicking retrospective, sure to set any rail fan's heart pounding