The spread of Plains culture into the Basin-Plateau area has been described by Wissler, Lowie, and others, the emphasis usually being upon traits of material culture. Less research has been devoted to the impact of equestrian life and the pursuit of the buffalo on the social structure of the people of the Intermountain area. This is in itself surprising, for a great deal of conjecture has revolved around just this question, but in the course of research upon the societies of the Plains proper. Such inquiry has often attempted to compare Plains societies of the horse period with those of the pre-horse era, revealed through archaeology and ethnohistory. In this volume, we attempt to approach the problem through both ethnohistory and a type of controlled comparison. That is, using the mounted, buffalo-hunting Shoshone and Bannock as our example, we will relate their social and economic life not only to the Plains, but to the Basin-Plateau area to the west and to their unmounted colinguists who resided there. In this way, we may analyze similarities and differences and attempt to answer the question of whether certain basic social modifications did indeed follow from the buffalo hunt. The Indian inhabitants of western Wyoming and southeastern Idaho, the subjects of this study, have their closest linguistic affinities with the peoples to the west. The languages of this area are well known and we need only briefly recapitulate their relationships. Those peoples of the Basin-Plateau area known in the ethnographic literature as Shoshone, Gosiute, Northern Paiute, Bannock, Ute, and Southern Paiute all belong to the Uto-Aztecan linguistic stock and are thus related to the Hopi and Aztec to the south and the Comanche of the southern Plains. Within this larger grouping a number of subfamilies have been identified. Those with which this report is concerned are the Shoshone-Comanche and Mono-Bannock. The Shoshone-speaking peoples of the Basin-Plateau area include the Northern, Eastern, and Western Shoshone and the Gosiute, all of whom speak mutually intelligible dialects. The area occupied by this population extends from the Missouri waters on the east to beyond Austin, Nevada, on the west, and from the Sawtooth Mountains of Idaho to southern California. There are no sharp linguistic divisions within this vast region, and phonemic shifts are gradual throughout its extent. The Mono-Bannock division comprehends the speakers of Northern Paiute living in the region east of the Sierra Nevada from Owens Lake, California, to northeastern Oregon and the Bannock Indians of southeastern Idaho, who stem directly from the eastern Oregon Paiute.