- California Doubling: The Mexican state of Durango stands in for post-bellum Texas.
- The Cast Showoff: Before filming began, John Huston and Burt Lancaster took Lillian Gish out to the desert to teach her how to shoot, which she would have to do in the film. However, Huston was astounded to discover that Gish could shoot more accurately, and faster, than both he and Lancaster, who thought themselves expert marksmen. It turned out that early in her career Gish was taught how to shoot by notorious western outlaw and gunfighter Al J. Jennings, who had become an actor after his release from a long prison sentence for train robbery and was in the cast of one of her films. She found that she liked shooting and over the years had developed into an expert shot.
- Creator Backlash: John Huston considered this one of the least satisfying movies of his filmography.
- Executive Meddling: John Huston was constantly battling with the Hecht-Hill-Lancaster production house, which financed the motion picture. They wanted a more commercial and less controversial film, while Huston wanted to make a statement about racism in America. The result is that neither got exactly what they wanted.
- Fake Mixed Race: Audrey Hepburn's ancestry is fully European, and here she plays a white-Native mix.
- Hostility on the Set:
- According to Audie Murphy's biographer Don Graham, the script called for Burt Lancaster to slap him. That enraged the war hero to such a degree that witnesses thought that Murphy, who carried a gun, might have killed Lancaster under different circumstances. John Huston eventually defused the situation.
- Lancaster and Murphy were engaged in an invitational tournament at a new golf course near Durango. Huston had an airplane filled with 2000 ping-pong balls with anti-Mexican and profane language and had them dropped all over the course, making it impossible to continue as none of the players could find their golf balls. Lancaster, who co-sponsored the event, was furious with Huston.
- Troubled Production:
- The film's projected budget of $3 Million expanded to $5.5 million. The original screenwriter JP Miller was replaced by Ben Maddow, the original director Delbert Mann was replaced by John Huston, and plans for Richard Burton in the role that eventually went to Audie Murphy were scrapped when Burton demanded equal billing with Burt Lancaster, with the latter refusing (as he was also producer on the picture).
- Production was suspended for several months in 1959 after Audrey Hepburn broke her back when she fell off a horse while rehearsing a scene. Although she eventually recovered, the accident was blamed for a subsequent miscarriage she suffered. According to several published biographies of Hepburn, she blamed herself for the accident and subsequently all but disowned the film, although she did complete it when she was well enough to return to work. Hepburn took the next year off work in order to successfully have a child, and returned to the big screen with Breakfast at Tiffany's.
- What Could Have Been:
- Tony Curtis refused the role of Cash Zachary, feeling that at this point in his career, he no longer needed to play second leads. Richard Burton, Kirk Douglas and Robert Mitchum also passed on it.
- Bette Davis turned down the role of Mattilda Zachary, because she didn't want to play Burt Lancaster's mother.
- Natalie Wood was considered for the role of Rachel Zachary.
Trivia / The Unforgiven