The mule is a hybrid offspring of a male donkey, commonly known as a jackass, and a female horse. Characterized by long ears, a braying voice, and a short mane, this patient and sure footed animal has been used as a beast of burden throughout the world. Its size and strength gained from the horse and its stamina and intelligence inherited from the donkey made it the most widely used animal for hauling men and material from the east, thus allowing settlement of the west. The mule was particularly useful in the eastern Sierra, where mining was done in steep mountainous terrain. In the late 1800's, twenty mule teams hauled 36 ton wagons of borax from Death Valley to the railhead near the present day town of Barstow.