John Wayne very much wanted the role of Wild Bill Hickok, which he felt certain would make him a star, but director Cecil B. DeMille wanted Gary Cooper instead.
An excellent horseman from his youth in Montana, Gary Cooper did most of his own riding stunts, including the shot where he rode hanging between two horses.
The cavalry sequences were shot with members of the Wyoming National Guard. Two guardsmen were badly hurt during filming of a charge scene.
Anthony Quinn later married Cecil B. DeMille's daughter Katherine.
Anthony Quinn told Cecil B. DeMille that he spoke fluent Cheyenne. Quinn's description of the Custer battle is gibberish, but DeMille was impressed.