Producer George A. Hirliman attempted to revive the popular "Rex, King of Wild Horses" films of the 1920s with his 1938 release King of the Sierras. The magnificent black stallion Rex (or his descendant) carries the film's "romantic" plotline, as he regularly purloins the mares and fillies under the protection of his equestrian rival, the white stallion Sheik. Framing the story is old-timer Hobart Bosworth, who recalls the adventures of Rex and Sheik to his wide-eyed grandson Harry Harvey Jr. The film is beautifully photographed (by Jack Greenhaigh Jr.), a fact that glosses over the multitudinous faults in W. Scott Darling's screenplay. Though it pleased the crowd in 1938, King of the Sierras did not inspire a series of "Rex" vehicles.