Continuity mistake: Approximately 46 minutes into the film, Robert Preston is testing a new bullwhip. The whip is in his left hand as he brings his arm back and cracks the whip. He brings the left arm back for a second crack, and the shot changes to a closer angle just as he brings the whip down, only now it is suddenly in his right hand and not the left. The editing, the sound effect, the arm swing all seem perfectly coordinated, except that the whip changed hands between camera set-ups.
Continuity mistake: In the train scene near the end, the two flat wagons and caboose separate from engine and coal tender, yet when they derail there are 2 passenger cars with the engine.