During their voyages, explorers encountered new Aboriginal nations. Pierre Gaultier de la Vérendrye went west to find out whether the river that flowed near the Mandan's territory (North Dakota) could be used to reach the "Western Sea." On the way, he met the Cree and the Assiliboilles [Assiniboine], allied nations whom he entreated not to deal with the English at Hudson Bay, and to remain loyal to the French fur traders. Once he arrived among the Mandan, a nation with whom the French had never had any contact, friendly relations were established.

Journal of La Vérendrye
Journal of an expedition in the West, by Pierre Gaultier de La Vérendrye, addressed to Charles de Beauharnois de la Boische, July 1738—May 1739