Prior to European settlement of North America, bison were one of the most numerous large grazing animals, numbering between 30 and 60 million.
Historically, plains bison ranged from the Allegheny Mountains to the Rockies, and from Canada to Northern Mexico. Woodland bison ranged farther west and north into Northwest Territories of Canada. Download a North American bison range map [PDF, 178KB].
Bison were extirpated east of the Mississippi River by the early 1830s. Systematic reduction between 1830 and 1874 destroyed the southern Plains herds. Between 1876 and 1883, the northern Plains herds were destroyed. A census in 1905 indicates that there were 835 wild bison and 256 bison in captivity.
A combination of government and private efforts in the U.S. and Canada brought the bison back from the brink of extinction with sanctuaries, zoos and parks becoming safe havens for bison and helping increase their numbers.March 02, 2011