In 1851, the area in question was included in a treaty with the United States for the first time, namely in the Fort Laramie treaty. This peace agreement defined territories for the tribes, in an effort by the US to establish peace among them and protect its own settlers. The treaty was signed by representatives of the numerous tribes of the Plains and mountainous West, including Crow, Lakota, Cheyenne and Arapaho; Gros Ventre, Mandan, and Arikara; Assiniboine and other nations. Intertribal warfare had been common among the tribes to gain social and economic advantages in furs, slaves, horses, hunting grounds, and other interests. They continued to wage war against each other into the late 19th century, conducting affairs separate from interaction with US forces and representatives.