Commercial hunting (remember Buffalo Bill?) and diseases caused and transmitted by domestic cattle led to the near extinction of the Bison with a population of may be 500 animals by 1889.
In the mid 20th century efforts were taken to reintroduce the bison and protect it - nowadays the estimates range from 30 000 to 200 000 animals. It's unclear how many are raised on farms for commercial purposes and how many are living in the wild, usually National Parks and similar protected areas. However, there are, at any given time, efforts by lobbyists to get the protection status removed or at least get certain numbers allocated for the purpose of trophy hunting.