Visible crew/equipment: At Lees Ferry when the stagecoach is crossing the river, there is a shot from on top of the stagecoach. As the camera pans over to the river, a clear shadow of the camera and its film magazine are visible.
Revealing mistake: When we see a wagon with a woman and several children in it, the horses get spooked and run. A woman is seen desperately trying to stop the runaway horses. In the next scene you can see the children are not real and the woman is a man dressed in a woman's dress, obviously a stunt man used for that scene.
Continuity mistake: When Cagney jumps onto the train in a wide shot, the steel car at his back is visibly taller than the wooden car he is facing. In the following close-up, the steel car has morphed into a shorter wooden car, same height as the other.
Other mistake: Just after newlyweds Gil and Lana arrive at Gil's small log cabin, they are visited by a Native American named Blue Back, who brings them a side of venison. Even though it has been pouring rain outside for hours, Blue Back is perfectly dry when he enters the cabin.