Nice Athern F unit :)

Oh ya. One of my favorite designs besides the old steam loco's. From what I saw on the History Channel about these particular trains is they were originally work horse trains in the train yards to help move cars around because they didn't think diesel was going to have the same power as steam loco's. But when the big steam engines were starting to become obsolete they took a closer look at diesel trains and started to use the engines as passenger trains.

There was a bit of resistance to diesel locomotives and it wasn't without good reason. The early examples we fussy, far fussier than steam if you can imagine. Getting to the 1940's the war effort had advanced internal combustion technology by great leaps. By the late 40's to the early 50's the railroads went through quite a bit of cost cutting moves and it was realized that the labour and fuel costs for operating a steam engine verses a diesel were quite large with the effects of post-war inflation. Also, there were issues with just how HUGE steam engines were getting as they weren't as scalable as internal combustion locomotives. Diesels also were 'NEW', so they often displaced some of the grander steam power on the premiere passenger trains as a way to make a road look prosperous and 'with the times'. Progressive roads rapidly went through dieselisation during this transition era and most had completely done so by 1960, though there were some holdouts until the mid 70's, mainly tiny class II and III roads, private industry and tourist. Today the only Class I road in the US that still operates a steam engine 'fleet' is Union Pacific with #3985 and #844.