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 Yosemite Sam goes to Bugs Bunny after he tells Sam to "shut up", you can see there is a glass beside Bugs on the counter. In the next shot, the glass has disappeared, and in the shot after that, it is back again.
Continuity mistake: When Brigade at the end of the movie tells Boone that he'll be the one to get him, Mrs Lane's hair is on/off her shoulder between shots. (01:10:35)