Over the weekend I posted a video history of EMD using S scale models to represent many of the important locomotives. The post was in the S Scale section of the forum, but several viewers suggested that more train enthusiasts might find the topic worthwhile despite the use of 1/64th scale models. Part of the reason for posting was to promote S scale, but the main theme was history of the company that got American railroading to abandon steam in favor of diesel locomotion. If you don't mind the references to S scale, you might find the video interesting and informative.
https://www.youtube.com/watch?v=G30hgCwL4x0
Terry O'Kelly