Factual error: At the end of the movie, the narrator says that Ike Clanton was shot and killed during an attempted bank robbery. Ike Clanton was actually killed while attempting to flee from Detective Jonas Brighton who was sent to arrest him for the crime of cattle-rustling.
Continuity mistake: During the fight at the OK corral, Doc Holiday has a double barrel shotgun but he shoots it three times, once in the air to spook the horse, once again to shoot the guy behind the horse, then the scene changes and he shoots another guy with the same gun without reloading.
Factual error: Billy Breakenridge in real life was a large man who was almost certainly not gay. He certainly wasn't effeminate as the film makes him out to be and he was known as a good shot and a tough individual.
Continuity mistake: The scene where Ed says "there's three of them over there" referring to the Cowboys, but when the shot is shown there's actually four Cowboys.
Continuity mistake: After shooting up the wedding near the start, they are sitting at the table eating the feast. As the camera shows Curly Bill's plate the food on it keeps changing.