The ranch house used for the McCandles ranch is the same house used for the Chisum ranch in Chisum (1970), a John Wayne western made a year earlier. Note the scenery around the ranch.
This was the first of only three John Wayne films (the others being Cahill U.S. Marshal (1973) and McQ (1974)) to receive AA certificates by the UK censor, meaning that they could only be seen by persons 14 and over. All other Wayne movies were rated 'A' (PG) or under.
In 1971, owing to the success of this film, John Wayne was #1 at the US Box Office for the last time.
Director George Sherman was a friend of John Wayne dating back to their days in the 1930s making westerns at Republic Pictures. By the time of this film, however, Sherman was aging and not in the best of health, and had a difficult time shooting in the wilds of Mexico, where much of the movie was filmed. On the days when Sherman was unable to shoot because of his health conditions, Wayne took over direction, but when the film was completed he insisted that Sherman alone be credited as director.