"Neither snow nor rain nor heat nor gloom of night stays these couriers from the swift completion of their appointed rounds." While working on this book， Craig Brown traveled to the Grand Canyon to observe the only mule train delivery route in the United States. MULE TRAIN MAIL introduces readers to Anthony Paya， who wears a cowboy hat， chaps， and spurs， and leads a train of mules on a daily three-hour trek down into the Grand Canyon to bring mail to the townspeople of Supai.