The slaughter of millions of bison in the latter half of the 1800s resulted in the near extinction of the species. The southern bison herd was exterminated in the 1850s and 1860s, while the northern herd was decimated by the early 1870s.

Because of the work of zoologist William T. Hornaday, naturalist George Bird Grinnell, Theodore Roosevelt, and others, about 30,000 bison live in North America today. The wood bison is threatened by disease, genetic hybridization, and shrinking habitats.