They traveled to the mountains to gather berries and roots. Ibid. The Yakamas’ religion and culture also depended on certain goods, such as buffalo byproducts and shellfish, which they could often obtain only through trade. Id., at 61a–62a. Indeed, the Yakamas formed part of a great trading network that stretched from the Indian tribes on the Northwest coast of North America to the plains tribes to the east. Ibid.
The United States’ representatives at the treaty negotiations well understood these facts, including the importance of travel and trade to the Yakamas. Id., at 63a. They repeatedly assured the Yakamas that under the treaty the Yakamas would be able to travel outside their reservation on the roads that the United States built. Id., at 66a–67a; see also, e. g., id., at 66a (“ ‘[W]e give you the privilege of traveling over roads’ ”). And the United States repeatedly assured the Yakamas that they could travel along the roads for trading purposes. Id., at 65a–67a. Isaac Stevens, the Governor of the Washington Territory, told the Yakamas, for example, that, under the terms of the treaty, “You will be allowed to go on the roads, to take your things to market, your horses and cattle.” App. to Brief for Confederated Tribes and Bands of the Yakama Nation as Amicus Curiae 68a (record of the treaty proceedings). He added that the Yakamas “will be allowed to go to the usual fishing places and fish in common with the whites, and to get roots and berries and to kill game on land not occupied by the whites; all this outside the Reservation.” Ibid. Governor Stevens further urged the Yakamas to accept the United States’ proposals for reservation boundaries in part because the proposal put the Yakama Reservation in close proximity to public highways that would facilitate trade. He said, “ ‘You will be near the great road and can take your horses and your cattle down the river and to the [Puget] Sound to market.’ ” App. 66a. In a word, the treaty negotiations and the United States’
