Bison Skulls in Detroit, 1892 This is a nn amazing photograph from 1892 of a pile of American bison skulls in Detroit, Michigan, waiting to be ground for fertiliser or charcoal. What Happened To American Bisons in 1800's At the beginning of the century (1800's), tens of millions of bison roamed North America. Pioneers and European settlers slaughtered an estimated 50 million bison during the 19th century. This overhunting was in part motivated by the U.S. government's desire to limit the range and power of indigenous plains Indians whose diets and cultures depended on the buffalo herds.The overhunting of the bison reduced their population to hundreds. Railroads were advertising "hunting by rail", where trains encountered large herds alongside or crossing the tracks. Men aboard fired from the train's roof or windows, leaving countless animals to rot where they died. Today; As of July 2015, an estimated 4,900 bison lived in Yellowstone National Park , the larges