Advertised as the first movie shot entirely in Arizona, which it wasn't (the first movie shot in Arizona, that is) by several country miles and years, and featuring Arizonians such as ten-year-old Ruth Reece, a singer on radio station KOY, and Doc Pardee, a horse trainer who also had the reputation as the fastest talking rodeo announcer in the profession, the story takes place on the Coburn Ranch (played by the real Gillespie Ranch in southern Arizona), a cattle empire that stretches over many thousand of acres, but has fallen on hard times because the owner, "Wild Bill" Coburn, owes the government $80,000 in back taxes. Coburn sees two solutions to the problem; one is for his thoroughbred, Sky Lancer, to win the Arizona Derby, and the other is to have his daughter Georgia marry the wealthy "Van" Van Wyck, whose horse, "The Gem" is Sky Lancer's only rival for the derby purse. Roving cowhands Pokey and Pee Wee arrive at the ranch and are given jobs because Pokey is the only man who can ride Sky Rex (Rex Jr., who may or may not have been the son of the original Rex, King of the Wild Horses), an outlaw horse just brought in from the range. Pokey falls in love with Georgia, and makes friends with little Juanita, Coburn's other daughter. Pokey and Georgia accidentally discover that Sky Rex can beat Sky Lancer but keep the information to themselves. Van Wyck, determined that Sky Lancer lose the race so that Georgia will have to marry him to save the old homestead, poisons Sky Lancer on the morning of the race. Georgia and Pokey race to the track with Sky Rex. Can an untrained wild horse of the range win the Arizona Derby racing against thoroughbreds? Does Tarzan go bare-footed in the jungle?