What it is
The American bison is a heavy grazing bovine of North American grasslands. IUCN lists it as Near Threatened. Most animals alive today are in commercial herds; conservation herds that are managed as wildlife are much smaller.
Range
Once from northern Mexico through the Great Plains into Canada. Wild or semi-wild herds now occupy scattered parks and reserves; the species no longer moves as a continental migrant.
What happened
Indigenous nations hunted bison for millennia without collapsing the species. Nineteenth-century market hunting, railroads, and U.S. campaign policy reduced the plains population from an estimated tens of millions to a few hundred by the 1880s. Ranching and park herds then rebuilt numbers. The animal survived; the free-ranging ecology did not.
When / status
Still here, mostly as a managed animal. IUCN Near Threatened.
Human role
Industrial hunting and settlement almost erased it; later ranching and reserves kept a remnant.
Sources
IUCN Red List (Bison bison, Near Threatened); historical plains-bison estimates (order-of-magnitude).