Uncredited - Frank Gorshin at the start of his career, as Billy. His character was Widmark's younger brother.
DeForest Kelley rather famously told an anecdote about the filming of this movie in his later years on the Star Trek convention circuit, about the time Princess Sofia of Greece was visiting the set and Kelley flubbed a scene by falling over a chair onto his backside and saying, "Oh, shit," in front of the princess. Henry Fonda told him the following Monday not to worry about it because he had danced with the princess over the weekend and ascertained that she had no idea what "shit" meant. This did not stop Kelley from getting a standing ovation at the commissary when the cast and crew broke for lunch.
Director Edward Dmytryk tells in his biography that Hank Fonda was such a fast draw with his six shooter that he (Dmytryk) had to slow up the action so the audience could savor it properly.
Richard Widmark and Henry Fonda appeared in five movies together, the others being How the West was Won (1962), Madigan (1968), Rollercoaster (1977) and The Swarm (1978). They were both married to the same woman, the socialite Susan Blanchard.