Originally, Laird Cregar was cast in this film in an undetermined role (possibly that of Doc Murdoch), but was unable to do the film due to an unfinished other project. He was replaced by George 'Gabby' Hayes, but Hayes then became ill and was himself replaced.
Studio publicity noted that Fox contract star Henry Fonda had served as technical adviser on the film, due to his experience as a young man working as a lineman. Fonda's "technical advisory" capacity was most certainly a publicity fiction, and in any event Fonda was not credited on the film itself.