Factual error: When Billy The Kid is taking a bath and dictating a letter to Doc, intended for the governor, he says he is in the Mexican village of Juarez. This town was actually named "Paso del Norte" at the time, it wasn't until 10 years after the events depicted in the film that it was renamed "Ciudad Juarez."
Factual error: The events in the film take place in mid-1929, as evidenced by the first Academy Awards being presented in May. However, Wyatt Earp went to the happy hunting grounds in January of that year.