In the 1500s, the Kootenai came into Montana from the north. The Salish and Pend d'Oreille migrated in from the north and northwest, venturing south to the Jefferson River/Missouri Headwaters and eastward. Major population shifts started in the early 1600s, bringing several new tribes into Montana. With horses of Spanish origin, the Shoshone migrated into Montana from the Great Basin and hunted buffalo, becoming the dominant tribe in the area. However, the arrival and expansion of European settlers on the east coast pushed Native Americans west, in a domino effect that extended all the way into Montana. The Crow migrated into Montana from the east in the 1600s, followed by the Blackfeet, Gros Ventre, and Assiniboine in the 1700s. With the acquisition of guns and horses, the Blackfeet became the dominant tribe on the plains in the 1700s. The Shoshone were largely pushed back over the continental divide into Idaho, but still ventured into Montana hunting and foraging. By 1800, the Missouri headwaters and much of southwest Montana was a crossroads frequented by the Lemhi Shoshone, Bannock, Nez Perce, Flathead, Crow, Sioux, and Piegan Blackfeet.