This film centers on the conflict between the fictional "Tomahawk & Western RR" and rival stagecoach lines. 

The film opens with some spectacular footage of Denver & Rio Grande's #20, which was gussied up as the "Emma Sweeny." It pulls a short train with D&RGW Combine #212 and Caboose #0409. Engine #20 today is owned and operated on occasion by the Colorado RR Museum. Combine #212 has been converted into a concession car and is in use on the Durango & Western RR and Caboose #0409 is now on display in Disneyland Tokyo. 

We see the train entering the High Line on what is now the Durango & Silverton route. 

The town of "Epitaph" is actually Silverton, CO and the depot now serves as the terminus for the Durango & Silverton RR. 

As the Emma Sweeny is pulled by horses out of town what you are now seeing is a studio-built replica that is seen for much of the rest of the film. This survived after filming and today is on display in Santa Rita Park in Durango. 

This replica engine was also hauled out on location and back to Fox Studios in Century City, for use in the campsite dance number on stage. 

After they disassemble the locomotive for transport over the mountains and reassemble it on the other side (quite the imaginative leap), we switch back to the real D&RGW #20. 

We get the ol' bad guy horse-transfer to the engine and rooftop brawl as the train rounds Rockwood Cut for the High Line. 

With a boiler full of bullet holes, she's out of steam just shy of town (Silverton again), so the whole town teams up to come to the rescue. 

Soon enough it's time to fire her up again! For this final scene, Flatcar #1026 and Boxcar #3745 were added.