Factual error: In the scene just before the fight at the O.K. Corral, Wyatt is talking to his brothers and Doc on the porch of the town marshal's office. There is an American flag flying behind him with 50 stars on it when in fact there were only 38 stars on the flag in 1881.
Factual error: During the gunfight in the lot behind the OK Corral, Tom McLaury is firing a six shooter at Doc just before Doc fires his shotgun in the air to scare Tom's horse away. The mistake is that Tom McLaury wasn't armed during the actual gunfight. He was shot by Doc while he was reaching for the rifle he had stored in his saddle. (01:14:58)
Factual error: Three of the Earp brothers arrived in Tombstone on December 1, 1879. They served as lawmen during 1880/81 and fought the Cowboys in the famous gunfight on October 26, 1881, They left the area in April 1882. In the movie the Earp's arrive in Tombstone in 1881 and ride past Boot Hill Cemetery. The tombstone displaying one of the most famous epitaph ever written is visible: "Her lies Lester Moore, Four slugs from a .44, No Les, No more." The problem is that Lester Moore wasn't killed until 1884. So it's impossible for his tombstone and famous epitaph to be in Boot Hill when the Earps arrived.
Factual error: In the scene when Virgil returns to the Oriental after being shot, Wyatt and Morgan are sitting at a table eating Chinese noodles with vegetables, among which is broccoli. Broccoli was practically unknown in the United States until it began to be commercially cultivated in California in the 1920s.
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.
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.