AllMovie

Each episode of Trains Unlimited offers viewers an in-depth portrait of a facet of world rail travel. Through the use of extensive footage and interviews with experts, this series brings the past, present, and future of these great machines to life. In this particular episode, viewers consider the largest steam engines ever built, including the Union Pacific's Big Boy. Bigger and bulkier cargoes as well as new competition from shipping led to an unquenchable thirst for power. These giant machines are the result of that thirst.