As a movie, enjoyed it - it was on TCM as part of Gloria Grahame's day on Summer Under the Stars, late last night or this morning. But as others have noted, the stock footage and the backgrounds in the process shots are from all over.
A fair amount on the PRR - as the OP noted, the Trenton bridge in the background. They also pass K Tower in Washington, in a view from the cab. Later there's a passenger train with what looks to be a PRR striped loco (hard to tell - it's printed really dark), with a blunt-end observation car.
Agreed that it's Albuquerque - they use two or three times the same footage of a train arriving - but only after the locomotives have passed.
There's a B&O train crossing the Potomac at Harpers Ferry.
A shot early on, from the cab - the train is approaching an overpass that carries a road above the tracks. The film appears to printed flopped - I think the bridge says 1910. After the bridge, there's what looks to be a small station on the left (or right, in reality). It's a four-track main - no electrification.
David
