Perhaps others are familiar with this 1948 film by the Association of American Railroads. I found it fascinating and lots of views of what we now love in O-gauge: Big steam, steamline diesels, semaphores, etc. Lots of good views in the former New York Penn Station as well. Lots of prototype Lionel and MTH trains!
http://www.youtube.com/watch?v=C_znc4SEO08