King of the Wild Stallions (1959)

Martha Morse, a young widow, must raise $500 within a few days or lose her government-grazing rights and her ranch. Matt MacGuire, an unscrupulous neighboring rancher, blocks all her efforts to raise the money so that he can grab her property. McGuire also seeks a wild black stallion which has been seen roaming the nearby hills. A large reward has been posted for the capture of the horse. He learns that the horse has been captured by Martha's young son, Bucky. Stymied at every turn, Martha turns to her only friends, Randy Burke and his pal Idaho.