http://www.dailykos.com/story/2012/05/10/1090409/-Indians-101-The-Bozeman-Trail-
In 1851, the United States called a treaty council at Fort Laramie, Wyoming which was attended by 8,000 - 12,000 Indians from the Cheyenne, Arapaho, Shoshone, Crow, Assiniboine, Arikara, Gros Ventre, Mandan ... the need to find food and clothing.