Factual error: Towards the end when the cavalry uncovers the American flag, it has 50 stars.
Continuity mistake: When Rick Nelson tells Angie Dickinson to throw the plant pot through the window to distract the gunmen who threaten John Wayne he seems to have had a hair cut between scenes as his sideburns are halved by the time he reaches the street and grow again later.
Visible crew/equipment: Michael Pate is walking down the street in this western and as he passes a shop window you can see all the camera crew, the director, the arc lights etc.
Continuity mistake: When Sam is counting to five when riding his horse, he runs into a telegraph pole and loses his guns in the process. But when he catches up with Bugs on the train, he is holding his guns again.
Continuity mistake: The last night before the supposed arrival to Santa Cruz, Boone approaches Mrs. Lane. The moonlight (actually a rather obvious day-by-night) shines on her fully, but as the camera switches to a close-up, suddenly there are all sorts of shadows of foliage over her blouse. (00:57:20)