Rooster Cogburn wields a Winchester 1892 rifle with a looped lever and a Colt 1873 SAA revolver. Le Bouef carries a Sharps single-shot rifle. Mattie uses a Colt-Walker 1847 "Dragoon" revolver. Chaney uses a Henry rifle.
Stunt double Jim Burk performed the entire scene where Rooster Cogburn charged Ned Pepper's gang of horseback. John Wayne was only seen briefly in close up, riding a trailer.
The character of Mattie was supposed to be 14. Kim Darby was going on 22 when the film was made.
The character of Rooster Cogburn was supposed to be around forty. John Wayne was 61 when the film was made.
The gang's cave hideout (beds partially intact), snake pit, and various prop rocks can still be seen on private property outside Ouray, Colorado.
The only film for which John Wayne ever won an Oscar.
The scene near the end where Rooster Cogburn (John Wayne) and Ned Pepper's gang meet in a field and Pepper (Robert Duvall) is shot was filmed in a clearing near the top of Owl Creek Pass outside Ridgway, CO. The field is off the road to the left and is very easy to find.
This is the (uncredited) film debut of Wilford Brimley.
Wayne's eye-patch is worn over his left eye, the same eye over which his long-time director John Ford wore his.
When submitted for a rating from the MPAA in 1969, the film was given an "M". The film was edited and re-rated "G".