The Last Outlaw.

On his way to Steer City, Buddy Hale rescues Janet Lane from a runaway horse. Unknown to Buddy, the woman's brother Ward just shot the sheriff. Heading a ring of indignant ranchers whose cattle are being systematically rustled, Ward suspects that the sheriff and Justice Bert Wagner are leading the gang of thieves. Justice Wagner makes Buddy sheriff and sends him to arrest his predecessor's murderer.