They said it couldn’t be done. It was too heavy, too long, it burned too much fuel, and would cost too much to restore. But they were wrong. Union Pacific, Big Boy #4014, now holds the title of the Worlds largest operating steam locomotive. This locomotive underwent a frame up rebuild and is now better than new. She came to Laramie WY. May 4th,2010. This is the first time out since the complete rebuilt. Fist time under own power for 50 years.