All of the following is copied and pasted from the Wikipedia article about this film:

There are historical inaccuracies contained in the film depiction of the Gunfight at O.K. Corral:

• Virgil Earp was already a deputy U.S. Marshal when he arrived in Tombstone, while Wyatt had little, if any, legal authority.
• Wyatt came to Tombstone with a common-law wife, whom he later sent away to stay with his family—in order to get her away from opiates.
• The real gunfight was a 30-second long, face-to-face affair with only a few firearms, not a medium-range, heavily armed shootout as in the film.
• The real corral was considerably smaller and simpler than depicted in the film (or in the previous movie, My Darling Clementine)
• Johnny Ringo was not present at the OK Corral gunfight. He later killed himself.
• Ike Clanton brought murder charges against the Earps and Doc Holliday. The Cowboys claimed the Earps had killed the outlaws as they attempted to surrender. During the Spicer hearing, the coroner and witnesses presented conflicting evidence about whether the Cowboys had their hands in the air or guns in their hands or were trying to draw their weapon when the fighting started.
• Morgan and Virgil Earp were wounded and Holliday was grazed by a bullet. Wyatt was unhurt.
• Judge Wells Spicer ruled that the lawmen acted within their authority.
• It was Wyatt's younger brother Morgan, not James (Wyatt's older brother), who was ambushed and murdered in Tombstone. This occurred after the O.K. Corral gunfight, not before. Virgil Earp was also ambushed in Tombstone after the O.K. Corral fight. He survived the attack, but was left with a permanently disabled arm.
• The actual gunfight took place in a vacant lot behind the O.K. Corral, next to a boarding house and photography studio, not in the corral itself. It was not an "event by appointment", as the prearrangement between Billy and Wyatt the night before depicts in the movie. It evolved the morning of the fight as the Earps responded to the chaos and threats raised by Ike Clanton after drinking himself into a rage the entire night before.
• James Earp was the older brother of Wyatt and never involved in the law enforcement side of the family. He was present in Tombstone but worked as a bartender. Warren Earp was the youngest of the Earp brothers and bounced from Tombstone to California between 1880 and 1882.
• Ike Clanton was never the leader of the Cowboys. Old Man Clanton controlled the gang until he was killed in 1881 and leadership of the gang fell to Curly Bill Brocis and Johnny Ringo.
• The film introduces a romance involving Wyatt Earp and a fictional character (based on Lottie Deno) which played no factor in the actual gunfight nor did anything to advance the film's plot.
• Charlie Bassett was Wyatt's boss in Dodge City. The film portrays the relationship as the other way around. Bassett and Wyatt Earp were nearly the same age. The film portrays Bassett as a younger man compared to Wyatt.
• Doc Holliday did not directly follow Wyatt to Tombstone. He turned-up there sometime after Wyatt had already established residence.
• Doc Holliday saved Wyatt Earp's life, not the other way around.
• The real sheriff's name was John Behan, not Cotton Wilson. The sheriff was not shot that day, and the Clanton gang did not shoot one of their own for deserting.
• The shootout is portrayed in the film as a protracted, heavily armed firefight that took place at medium range. The actual event began in a narrow 15–20 feet (4.6–6.1 m) wide empty lot between the Harwood house and C. S. Fly's 12-room boarding house and photography studio. The two parties were initially only about 6 to 10 feet (1.8 to 3.0 m) apart, and the real gunfight lasted only about 30 seconds.

Good movie. I've newly, first time in decades, watched it, and enjoyed it. Very well acted. Exciting shootout! (See also here.)