Continuity mistake: When Colonel Marlowe blows the bridge near the end of the film, a pair of spectacular explosions ensue, tossing planks and beams into the air. However, as Hannah Hunter gazes at his retreating form, the bridge is still intact.
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.
Continuity mistake: In the first close-up of the big evil that is Billy's brother, Lee Van Cleef's face is lit under a totally different light (when he says "It ain't the money that Brigade wants. Not the money at all"). (00:50:05)
Continuity mistake: When Bugs is performing his shooting stunt in the saloon, you can see the entrance behind Sam has nothing between it. When Sam tells Bugs he's missed, we cut to Bugs who says "Wait!" and then return to Sam, and this time there are doors between the entrance.