Prior to production, United Artists had made it clear to director John Sturges that none of the primary roles were to be filled by actors who had played the same characters in Gunfight at the O.K. Corral (1957). Sturges believed that the roles of Virgil and Morgan Earp from the previous film were small enough that the same actors could do it again without harming the film's uniqueness. The studio agreed, and allowed Sturges to cast John Hudson and DeForest Kelley. Hudson had retired from acting in the early 1960s, and was unwilling to come back. Kelley was working on Star Trek (1966) and unable to break away. Thus, both Earp brothers were re-cast.

The movie depicts Tombstone to have a railroad with depot. The railroad did not come to Tombstone until 1903.

Wyatt Earp's giving Warshaw a chance to draw against him is taken from the story of Earp doing that with Florentino Cruz, who also said he'd been paid $50 for his participation in the assassination of Morgan Earp, according to the Stuart N. Lake book "Wyatt Earp: Frontier Marshal." However, in the movie, Earp empties six shots into Warshaw. The real Wyatt Earp kept only five rounds in his pistol, resting the hammer on an empty chamber for safety, according to the Lake book.

The historical "Vendetta Ride" on which this film is based was in fact a murderous rampage carried out with no legal authority. Previously, Wyatt Earp had relied on the legal system to bring the Cowboys to justice, but after the suspect in his brother's murder were freed, he decided to take matters into his own hands. He held the office of US Marshal at the time to enable the arrest of the Cowboys, but warrants were issued against him and his deputies for extra-judicial murder. In 1882 Pima County Sheriff Bob Paul rode to Colorado to extradite Wyatt, Warren and Doc back to Arizona. He served the warrant to a dying Doc, but not to the Earps with whom he was friendly. Later the same month Colorado Gov. Pitkin refused to honor Arizona's extradition request, allowing Earp and the others to leave the state.

Sheriff Jimmy Bryan is based on the notoriously corrupt County Sheriff John 'Johnny' Behan, a former lover of Wyatt's future wife Josephine Marcus (Josie). The reason for the name change is unclear.

Continuity

Near the end of the movie, when Wyatt leans on the door jamb at the Glenwood Sanitarium, the outdoor scenery lighting is noticeably turned up perhaps to cast a desired shadow as he steps onto the deck to speak with Doc for the last time.



Factual errors

In the gunfight, it shows only Billy Clanton, Tom McLaury and Frank McLaury in the OK Corral and the Earps outside. In reality, the gunfight took place in a vacant lot behind the OK Corral. In that lot were the Earp party, Billy Clanton, the McLaury's, Ike Clanton and Billy Claibourne along with two horses.

The film has the gunfight taking place on a perfect warm sunny day. It was actually overcast, cold with snow on the ground.

Although the opening text says that this version of the story is all true, large parts of the plot's claims are inaccurate.

Neither Virgil or Morgan Earp ever attempted to run for city marshal as depicted in the film.

Ike Clanton is depicted only witnessing the gunfight, not at all being in the line of fire. In reality, he was, he ran up to Wyatt right when the shooting started and Wyatt shoved him off, Ike ran away.



Miscellaneous

When Wyatt returns to town and steps off of the train, his legs give shadows in two directions on the platform.



Audio/visual unsynchronized

About 67 minutes in, when Wyatt Earp shoots the bottle of whisky, recently purchased and wrapped in brown paper, that Doc Holliday carries, the sound is of an empty bottle shattering, not a full one. Also, such a shot would make the bottle explode with considerable force, yet there is no trace of liquid or any shards of glass to be found anywhere.



Crew or equipment visible

During the nighttime scene when Wyatt and his posse are holed up in a ranch house playing poker, a piece of equipment reflecting light can be seen rising and lowering in the darkness outside the window behind Monte Markham's character Sheriff Sherman McMasters, who is seated in a chair in front of the window while the others play cards.

When Wyatt Earp shoots Ike Clanton, the latter flies backwards with considerable force. If you look closely, you can see the wire extending from him to the junction of the walls behind him; obviously a machine was used with a harness and wire to jerk him so quickly that he literally flies off his feet. The wire even reflects sunlight after the initial jerk.

Near the end of the film, when Wyatt and Doc ride up to the Federalie HQ, if you look at the bushes along the adobe wall of the building, you can see the pipes used to create fog for the night scene.



Character error

Doc claims to have killed men as a soldier between 1861 and 1865, but John Holliday was only 14 at the end of that time period, making him too young to be in the army. This inaccurate statement may be deliberate within the film, as Holliday often told lies to bolster his image (e.g. that he learned dentistry at Johns Hopkins University) because he wanted to conceal a shameful past.