Stage to Blue River (1951)

Marshal Whip Wilson and his pal, Texas, come to the aid of Joyce Westbrook after her father is killed by henchmen of a mysterious Mr. Blackwell, who is after the stage line contract left to Joyce. She tries to get a government mail contract, but one of the conditions is that her stage line must be proven safe. Whip, Texas and Ted Crosby have several battles with the outlaws, and Whip learns that attorney Kingsley is one of the plotters and, with the help of the postmaster, he discovers that Mr. Blackwell is really Sheriff Bill Preston.