How did the eastern Sahaptin peoples adopt customs from the Plains Indians?

During the late 18th and early 19th centuries, eastern Sahaptin peoples—such as the Nez Percé, Palouse, Cayuse, and Umatilla—adopted various customs from the Plains Indians primarily through trade-based interactions during seasonal journeys across the Rocky Mountains.12

This cultural exchange manifested in several ways:

• Material Culture: Sahaptin women began creating and wearing beaded dresses inspired by Plains styles, while men adopted feathered headdresses and other war regalia. Additionally, the use of tepees became popular among these groups.1
• Political and Social Organization: Unlike the more autonomous western Sahaptin groups, eastern tribes developed stronger political cohesion, often utilizing a tribal chief and council. They also engaged in intertribal marriages.2
• Warfare: Eastern Sahaptin groups adopted many customs associated with Plains warfare, including the practice of graded war honors and the hosting of communal victory celebrations and dances.2

These changes were facilitated by the acquisition of the horse in the early 18th century, which increased mobility and interaction with neighboring cultures.13