Although this is hardly the story of how the Pony Express got started, Iron Mountain Trail which is set in the 1850s California is good action packed western from Republic. It stars the last of Republic's singing cowboys Rex Allen with Slim Pickens as his sidekick. Pickens who went on to a successful career as a character actor, best known as the pilot in Dr. Strangelove, got his first real notice as Allen's sidekick in his westerns.
Rex is a postal inspector concerned that mail is not being delivered on time or at all with the clipper ship service from northern California in San Francisco all the way down to San Diego. He's ready to reward the government contract to the winner of a race from San Francisco to San Diego involving two feuding stage line owners and Grant Withers the owner of clipper ships.
But when Withers murders one of the two owners and frames the other it becomes a race not for a mail contract, but to save Forrest Taylor's life. Allen and Pickens have to get Roy Barcroft who is the mate on Allen's ship. Withers in a plot gambit stolen from the Warner Brothers classic The Oklahoma Kid where James Cagney's father is hung when a crooked judge is brought in to speed up due process and whisper in lady justice's ear. John Hamilton is the judge and a bit more should have been developed along those lines. There might have been originally, but the running time on this film is only 53 minutes and I suspect a lot got left on Republic's cutting room floor.
With that short a running time the emphasis is on action and there's plenty of it. Allen and Pickens nearly get shanghaied in San Diego and Pickens has a good turn as he can't quite shake the Mickey Finn he was fed.
This has to rank as one of Allen's better B westerns even with the short running time and holes in the plot. As for the Pony Express, you have to see the film for that.