Interaction with native peoples along the Missouri river basin was a crucial part of the Lewis and Clark Expedition. The Corps of Discovery depended on tribes for information, food, protection, and companionship. Additionally, Lewis and Clark were instructed by President Jefferson to "endeavor to make yourself acquainted, as far as a diligent pursuit of your journey shall admit, with the names of the nations & their numbers" (Jackson, item 47). As a part of this process Lewis and Clark compiled vocabularies of the native languages, as well as statistical and descriptive reports of the various tribes. Lewis and Clark also held formal councils with the Missouri river tribes, during which they informed them that the United States government had purchased the Missouri River basin from France, and that the tribes would henceforth be subject to the United States government. The image at the left, titled "Chief of the Blood Indians" by Karl Bodmer, depicts a chieftain wearing a peace medal like the ones given by Lewis and Clark as tokens of friendship.