Though hampered by a tiny budget, director William Witney manages to turn out one of the best of Republic's Rex Allen western series. Iron Mountain Trail features singing cowboy Allen as a non-singing U.S. postal inspector, assigned to find out who's been tampering with the ship mail on the California coastal route. The plot then goes off on another tangent, as Rex tangles with villain Mate Orrin (Roy Barcroft) in a race to prove that overland mail delivery is more efficient than delivery by sea. Naturally, Allen couldn't accomplish this without the help of his wonder horse Koko, who accordingly is given second billing in Iron Mountain Trail. Also on hand is Slim Pickens as Allen's comical sidekick, and he's pretty funny this time out.