After the Indian chief ran the train, Scott told the chief someday they will name a train after him. They did: the Santa Fe Super Chief.
The cards that Luke and Dan are playing with were made by the Bicycle Card Company founded in 1885, some 20 years after the movie is set.
The Santa Fe locomotive shown is #1, the C.K. Holliday. It's named after Cyrus K Holliday, the first President of the railroad.
A saloon tent that moved every week or so to keep within a few miles of a railroad crew would not drag a wooden floor except for maybe a small area. The saloon tent fight is on a wooden floor.
As Randolph Scott is leaving his old friends in Dodge City a mountain can be seen over his shoulder down the street. There are no mountains like that in Dodge City, Kansas.