I believe it was the thread on boiler rebuilds that lead me to a pretty interesting YouTube channel. It is a channel that has "Publicity films, newsreel & documentaries with a focus on transport and technology."
Here is one called "A Great Railroad at Work - 1942 American Railroads & Trains Documentary." It is a very comprehensive look at the New Haven Railroad in 1941 - 1942.
Here is called "Denver and Rio Grande Western Railroad in 1948 - Desert Empire"
Looking at the recommended videos on the right on the page will have other railroad videos on the channel.
On a side note, the D&RGW Desert video provided a link to a video not on this channel but about the narrow gauge at:
Enjoy everyone! If yall find a good video from this channel, post it up here!