”A product of U.S. Army-sanctioned mass slaughter of American bison in the 1800s, these bison skulls are waiting to be ground for fertilizer, most likely in the American midwest. The slaughter was so effective that the population of bison in the U.S. is estimated to have dropped from around 60 million in 1800 to as few as 750 in 1890.”
They were slaughtered as part of a U.S. Government Policy to rid the plains of the main food source of the tribes that lived there.
"…to rid the plains of the main food source of the tribes that lived there."
America has been stuck on genocide ever since white people landed here.