Bison came to North America during the Pleistocene Epoch via the Bering land bridge. Eventually they ranged from Canada's Great Slave Lake to Mexico and from eastern Oregon almost to the Atlantic. They especially thrived on the Great Plains where some 30 million formed the biggest mass of large mammals ever to tread the globe. Early French settlers who saw herds living near the East Coast called them bison because they looked like a European cousin. A later English naturalist described them as buffalo which name stuck, even though the term is more correctly applied to other types of wild oxen found in Asia and Africa.
Bison are susceptible to tuberculosis, anthrax, and brucellosis.
Their number was reduced to 750 in 1890. They were then protected and now number about 80,000. Bison live only in parks and reserves. MacDonald, David. 1984. Encyclopedia of Mammals.