Here's an old Union Pacific documentary one its last steam locomotives. The famous Big Boy takes the center stage through out with some spectacular footage.
I found that interesting, not only the big boy, but the locomotive that came before it, the challenger type locomotive, these two designs has almost the same appearance, but the only things that makes them different would be the number of drive wheels and the position of the union pacific shield number plate, but they have something in common as with other steam locos, they are both legends of a era long gone.
yes,and the reasons why the two locomotives were brought in was to increase freight train speed and to eliminate the need of two steam locomotives on one train which costs the railroad money and then there is the issue of the extra crew members which also would have to be paid, and finally the brutal grades that forced the previous locomotive's speed to be reduced to a crawl.