Factual error: When Wyatt (Kevin Costner) becomes the sheriff/deputy/policeman of Wichita, Kansas, you can plainly see mountains in the background - there aren't any around there.
Continuity mistake: In the scene where the Spaniard is beating up all the guys that Maverick paid off he ties one guy's neck to a post with his whip. As the shot changes you see the whip go only around his neck, but in the last shot of the scene it's around neck and post again. (00:36:00)
Continuity mistake: At the end the nasty man is out of bullets so the Bad girl throws him a bullet from her rifle. He puts the bullet in but fails to revolve the cylinder so of course he loses as you would have to thumb-cock and pull the trigger 3-4 times to get to the live ammo. Dumb, dead desperado.
Continuity mistake: Just after Samuel and Alfred say that they are going to enlist, Samuel has a weird looking face and notice Alfreds shoulder right behind him, then Susanna takes a few steps up the stairs very sad and Samuel walks a couple of meters towards her and then she leaves and then it switches to Samuel with the same funny looking face and Alfred is again right behind him. (00:24:20)
Continuity mistake: After Jack's second horse never comes back, neither do Ben's shoes. Were they with the horse that we don't know what happened to?
Suggested correction: The shoes are purposely removed and never seen again, as is the horse, by Jack. This is mentioned by the Indian tracking them.
Continuity mistake: When Mitch is trying to find the hand, Glen grabs the map. When he grabs the map there is a hole in it, but before he sets it on fire, the hole is gone.
Factual error: In the saloon at night, Ben Wheeler says, "I can't afford another Workers Comp claim". Workers compensation wasn't started in the United States until 1902. (00:10:25)