Buck did not read the newspapers, or he would have known that trouble was
brewing, not alone for himself, but for every tidewater dog, strong of muscle
and with warm, long hair, from Puget Sound to San Diego. Because men, groping in
the Arctic darkness, had found a yellow metal, and because steamship and
transportation companies were booming the find, thousands of men were rushing
into the Northland. These men wanted dogs, and the dogs they wanted were heavy
dogs, with strong muscles by which to toil, and furry coats to protect them from
the frost.
Decent research guide...scroll down.