A century ago the western half of the American Continent was unknown. Vast herds of buffalo and antelope swarmed over its rolling plains; elk and deer fed along its rivers; wild sheep and white goats clambered over its rocky heights; bears prowled through its forests; beavers built their dams and houses along every stream. Occasionally a group of Indians passed over the plains or threaded the defiles of the mountain ranges. A few years later the white man began to penetrate this wilderness. Beaver were growing scarcer, and men were forced to go further for them. So the trapper entered these unknown fastnesses and began his work.