“The Plains Indians constituted for a much longer time than we realize the most effectual barrier ever set up by a native American population against European invaders in a temperate zone. For two and a half centuries they maintained themselves with great fortitude against the Spanish, English, French, Mexican, Texan, and American invaders, withstanding missionaries, whisky, disease, gunpowder, and lead. It is true, as has been indicated, that their country, like Russia in the time of invasion, fought for them. . . .
Within the Plains area dwelt thirty-one tribes· of Indians. Eleven of these are typical Plains, tribes, possessing in common. in the highest degree. the characteristic Plains culture. These eleven tribes are the Assiniboin, Arapaho, Blackfoot. Cheyenne, Comanche. Crow, Gros Ventre. Kiowa, KiowaApache, Sarsi, and Teton-Dakota. They occupied the region from southern Canada to Mexico.”