Spencer Tracy was first cast as the secretary of interior Karl Shultz, but had a heart attack and was replaced by Edward G. Robinson, whose scenes were entirely photographed in studios, including the climatic meeting scene between Shultz and the Cheyenne chiefs, in which the background had to be done with screen process.
John Ford would not allow Sal Mineo to speak any English dialog in the movie due to the actor's Bronx accent.
According to Joseph McBride's "Searching for John John", John Ford was urged to cast Richard Boone and Anthony Quinn as the Little Wolf and Dull Knife characters, as both had Native American blood. Ricardo Montalban and Gilbert Roland, who were of Mexican descent, were cast instead.
According to both John Ford and James Stewart, Ford added the segment with Stewart in place of an intermission. Ford didn't want people leaving the auditorium to go the bathroom or concessions counter, even though the film was long, and so he came up with the Wyatt Earp segment. He later quipped to Stewart that the actor was the "best intermission" in the movies.
Average Shot Length = ~11.6 seconds. Median Shot Length = ~11.2 seconds.
Finnish certificate # 71202 delivered on 12-2-1965.
The "Cheyenne" are actually Navajo, telling dirty jokes in their native tongue.
The final duel between Little Wolf and Red Shirt was shot on the day that President John F. Kennedy was assassinated in Dallas, TX. Though legends say that John Ford, so saddened by the death of the first Irish president of the nation, mourned his death by halting the shoot on that day, production documents actually show that it was the only scene to be shot that day, and they moved from Utah in the afternoon as originally scheduled.
The role of Lt. Scott was originally offered to Jeffrey Hunter, who turned it town in order to star in the TV series Temple Houston. The part was eventually given to Patrick Wayne. Hunter's series only ran for one season before it was cancelled.
The usually puritanical John Ford contemplated filming a nude scene with Carroll Baker bathing in a river, but ultimately it wasn't shot.
When film critic Peter Bogdanovich visited the set to interview John Ford, he was introduced to Nancy Hsueh, who played Little Bird, whom Bogdanovich later cast in his first film, Targets. While Bogdanovich was on the set, Sal Mineo recommended the book "The Last Picture Show" by Larry McMurtry to him, which became his second film as director seven years later.