This film tells the story of the Kansas Pacific Railroad's attempt to expand westward just prior to the Civil War. As southern sympathizers attempt to sabotage the operation, Captain John Nelson (Sterling Hayden) is brought in to fight them off and keep the rail line on track. Most of the footage was shot on the Sierra Railroad in northern CA. 

Early track-laying scenes feature Sierra Railroad's famous #3 engine. 

A quick run-by shot features Sierra #3 and their often-used Hetch Hetchy #6 coach. Both of these are still in storage at Railtown 1897 in Jamestown, CA. 

The first of many sabotage attempts in the film involves the train running into some dynamited rails and bad guys posted up in the rocks above.

When we next see the train, the consist features Sierra Coach #6, a shorty flatcar and Coach Combine #5. 

Many more shots of the "Kansas Pacific" train featuring Sierra #3 are seen throughout the film as they continue to push westward. 

At several points midway through the film, we can briefly glimpse what appears to be an old Canadian Pacific 4-4-0 during track construction scenes. This is footage of CPR #30, which was borrowed from the 1949 film Canadian Pacific.

Some more nice shots of Sierra #3 as those dastardly saboteurs place boulders on the tracks. 

Another shot of CPR #30 pulling into a railroad camp taken directly from Canadian Pacific.

This shot of Sierra #3 pulling into the yard past a long line of hopper cars was reused several times in the film. 

As the Kansas Pacific line becomes active, our villains become more desperate and take to bombarding passing freight trains with cannon fire. This leads to some spectacular footage of Sierra RR #18 dodging explosions. 

Sierra #3 once again encountering torn up tracks. 

Shortly after being blown up, we see Sierra #18 back with the same freight consist, this time passing through a cut and being hit again by cannon fire. As it emerges from the smoke, we see it has magically transformed into Sierra #3 with a coach car. 

Once the bad guys are thwarted in a big fight scene, Sierra #3 is once again free to roam the countryside. 

The final scene takes place at the old Sierra freight depot in Jamestown, still in use today as part of Railtown 1897 State Park.