"This photo from the 1870s shows a man proudly standing in front of a mountain of tens of thousands of bison skulls - an iconic American species that was systematically slaughtered by the millions as European Americans colonized the west.

The US Army actively endorsed the wholesale slaughter of these animals for two main reasons: to remove any competition with cattle, and to starve Native American tribes who greatly depended on the bison for food. Without the bison, the resisting tribes of the Great Plains would either be forced to leave or die of starvation.”