- Actor Allusion: A belt buckle that Thorton sports in many scenes features the Red River D brand, an homage to John Wayne's first collaboration with Howard Hawks, Red River.
- Actor-Inspired Element: The bathtub scene was largely Robert Mitchum's invention. Members of the crew were laughing while it was being filmed at the idea of Mitchum being embarrassed in front of a woman.
- Cut Song: A group singalong similar to the ones in Rio Bravo was cut.
- Deleted Scene: A group singalong similar to the ones in Rio Bravo was cut.
- Dueling Works: John Wayne was disappointed that the movie was released at the same time as his next movie, The War Wagon. However, despite this film receiving generally poor reviews and being seen as old-fashioned, and out of tune with the times, both movies proved to be hugely successful at the box-office.
- Edited for Syndication: Misissipi's impersonation of a Chinese man is often cut from television broadcasts because it is considered racist.
- Hostility on the Set:
- Arch-conservative John Wayne did not get along with Edward Asner, whose politics were quite liberal, during filming, and constantly referred to Asner as "that New York actor". Asner later said he took the phrase as an anti-Semitic insult.
- According to James Caan, during a break he and Wayne got into an altercation over a game of chess. Caan accused Wayne of cheating. Robert Mitchum intervened and cooled things down.
- Prop Recycling: The same wanted poster of a man in a top hat smoking a cigar was used in The Sons of Katie Elder, also starring John Wayne.
- Real-Life Relative: The bartender that Robert Mitchum shoots in the saloon was played by his brother, John. John's character name was Elmer, but during the final shoot-out in the saloon, Robert made the mistake of calling his brother by his real name, "freeze it right there Johnny" he says as a warning not to get involved in the shooting.
- Recycled Script: Many situations and plot elements are very similar to those of the previous Hawks/Brackett/Wayne western, Rio Bravo, and to those of the next and last one, Rio Lobo. Some elements are inverted, e.g. instead of the hyper-competent Young Gun of Rio Bravo you had a youngster who is useless with firearms. The scene in which Thornton pushes one of McLeod's mooks through a door to be shot by his own men echoes a similar one from the first Hawks/Brackett collaboration, The Big Sleep. There also had been a scene similar to the one where Mississippi throws himself in front to the bad guys' horses that was cut from the final version of Rio Bravo, so to do it here, Howard Hawks bought the rights back from Warner.
- Real-Life Relative: The bartender that Robert Mitchum shoots in the saloon is played by his brother, actor/writer John Mitchum.
- Scully Box: James Caan has admitted he wore three-inch lifts in the movie.
- The Shelf of Movie Languishment: Filming was completed in February 1966, but it wasn't released until June 1967. The delay was partly because Howard Hawks wanted a re-edit at the last moment, and partly because Paramount Pictures didn't want to release it against another one of their own westerns, Nevada Smith.
- What Could Have Been: The original script for the movie was originally much darker, but Howard Hawks felt he didn't do downbeat too well, and decided on a re-write. Several dramatic key elements remained however, which were Cole's on and off paralysis, and the shooting and subsequent suicide of the teenager.
Trivia / El Dorado