John Wayne's character, Ranger Capt. Jake Cutter, is called Big Jake. Wayne later played Jacob McCandles in Big Jake.
Paul Wellman wrote the novel with Cary Grant in mind as Paul Regret. However, by the time the film was made in 1961 Grant was too old for the part, and would never have taken second billing to John Wayne.
Besides the name of William H. Clothier, the film's director of photography, another crew member's name that appears in the hotel registry signed by "Ed McBain" is that of Jack R. Berne, an assistant director on the film.
During much of the shooting, director Michael Curtiz was seriously ill (he died of cancer shortly after the film's release). On the days when Curtiz was too ill to work, John Wayne took over direction of the film, and when it was completed he told the studio that he did not want credit as co-director and insisted that Curtiz' name alone appear as director.
The final film directed by Michael Curtiz.
The last film of veteran cowboy actor Guinn 'Big Boy' Williams, who died shortly after its completion.
When John Wayne signs the hotel register as "McBain", one of the names in the register is William H. Clothier, the film's director of photography.