- Harry Carey
- Happy Cardigan
- Edwina Booth
- Caroline Hall
- Rex
- Rex
- William Desmond
- Milesburg Sheriff
- Frankie Darro
- Jimmie Williams
- Philo McCullough
- Stevens
- Yakima Canutt
- Yak [Chs. 1 & 3] / Bill Peters [Ch. 4]
- Joe Bonomo
- Stuffy
- Tom Dugan
- Oil Co. Director Warren
- Lafe McKee
- T.J. Hornbeck
- Bob Kortman
- Henchman Marno
- Edward Hearn
- Jed Williams
- Paul Weigel
- Oil Co. Director Larribee
- Frank Brownlee
- Oil Co. Director Bishop
- Olive Carey
- Nurse Lewis [Chs. 9-12]
- Robert Walker
- Oil Co. Director Allen
- Al Taylor
- Sheriff of Slocum [Ch. 1] / Deputy Thompson / Deputy Thompson [Chs - 4-7,8] / Henchman Dave / Horseman
- Dick Dickinson
- Rawlins [Ch. 7]
- Pete Morrison
- Oil Worker Brady / Crooked Deputy [Ch. 6]
- Dick Hatton
- Henchman Dodger [Chs. 1-5]
- Boris Karloff
- The Voice
- Tracy Layne
- Horseman [Ch. 1] / Oil Worker [Chs. 2 / 11-12] (uncredited)
- Cliff Lyons
- Deputy O'Brien [Ch. 1] / Wrangler Slim [Ch.1] / Shorty [Ch. 2] / Henchman [Ch. 4] (uncredited)
- Bud McClure
- Henchman
- Walter Miller
- Narrator of Opening Chapter Recaps
- Bob Reeves
- Henchman
- Charles Schaeffer
- Horseman Shorty [Ch. 1] / Deputy Johnson [Chs. 7-8] / Furniture Mover [Chs. 8,9] / Henchman (uncredited)
- Wes Warner
- Henchman (Chs. 1-5)
- Bill Wolfe
- Townsman
