Sergio Leone was approached to direct this film, but he turned it down since he was working on C'era una volta il West at the time.
CASTLE THUNDER: Heard several times during the rain after Jed and Rachel's picnic.
Reportedly, producer Leonard Freeman clashed with director Ted Post during production. One day Freeman showed up on the set, issuing orders and taking charge. Post wanted to confront him, but Clint Eastwood intervened. Eastwood spoke to Freeman, and Freeman left the set and didn't return. What he said was, "If you show up on this set again, there won't be a set ... won't be a cast, won't be a crew."
The character of Judge Adam Fenton was based in part on Judge Isaac Parker whose federal court in Fort Smith, Arkansas had jurisdiction over the Oklahoma and Indian Territories.
The first film produced by Clint Eastwood's Malpaso Company.
United Artists executives suggested experienced action film directors like John Sturges and Robert Aldrich, but Clint Eastwood gave the director's reins to Ted Post, who had directed twenty-four episodes of Rawhide and was very good at dialogue. Co-stars Charles McGraw, Ed Begley, Bruce Dern and Pat Hingle had all appeared in "Rawhide" episodes directed by Post.