Heart of the Rockies launched Republic's second season of popular "Three Mesquiteers" westerns. Returning to the fold are
Robert Livingston as Stony Brooke, Ray "Crash" Corrigan as Tucson Smith and Max Terhune as Lullaby Joslin. This time our heroes play modern-day cattle ranchers who are falsely accused of killing bears on the grounds of a national park. The boys seem to have plenty of motive, inasmuch as the bears are suspected of depleting their livestock. When it turns out that the real villains are a gang of smugglers, the Mesquiteers team with the park rangers to get their man (or men).
Robert Livingston was injured during production of Heart of the Rockies, forcing Republic to replace him with
Ralph Byrd in the next Three Mesquiteers opus,
Trigger Trio. ~ Hal Erickson, All Movie Guide