West of Rainbow's End (1938)

Tim Hart (Tim McCoy), a former Texas Ranger, comes out of retirement to avenge the death of Lightnin' Ed (Frank LaRue), his foster father, who had been sent to Rainbow's End, to investigate a series of train robberies. He senses that George Johnson (Walter McGrail) and his henchman, Speck (Bob Kortman), head the robbery gang, especially after Speck makes an ambush attempt on his life.

Unfortunately the movie West of Rainbow's End is not yet available on HBO Max.