One of the greatest expenses of the expedition was for the purchase of gifts and trade goods. Members of the Corps of Discovery relied on trade to initiate relationships with Indian people and to obtain critical resources from them. Lewis and Clark found native peoples engaged in extensive trade with each other and, directly or indirectly, with Europeans. Indian people expected Euroamericans to be traders, and some hoped that Americans would increase their supply of trade goods. "We want one thing for our nation very much, stated Arcawecharchi, a Yankton Sioux leader, "we have no trader, and are often in want of goods." In contrast, tribes along the Columbia River were already well supplied by Europeans active in the sea otter fur trade along the Pacific coast.
A willingness to trade was regarded as a gesture of goodwill, and the explorers also hoped to demonstrate the quality of American wares. Lewis packed a variety of trade items, ranging from thimbles, awls, and ribbon for women to firearms and tools for adult men. Unable to communicate verbally, the Americans often displayed these to the Indian peoples they encountered. Tobacco was the item they traded most widely as they traveled.
Trade was also critical to the survival of the American party, who needed food, horses, information, and clothing. They occasionally bartered with Native American women to obtain hats and garments for the party. When their supply of goods became exhausted, they exchanged their own possessions, treated the sick and injured with medical supplies, and offered animal hides. In return, Lewis reported that Indian people sought European blue glass beads and all manner of metal objects, such as brass buttons, knives, and other tools.
The Corps of Discovery spent their first winter near the Mandan and Hidatsa villages in present-day North Dakota. While there, they exchanged the services of their blacksmith for Mandan corn, beans and squash and purchased warm buffalo hides and moccasins.
