PBS
Pbs: The Native Americans
The Corps of Discovery came into contact with "Nearly 50 Native American tribes." This site from PBS discusses the tribes that had the most significant interactions with Lewis and Clark.
Library of Congress
Loc: Teachers: Journeys West
A series of lessons utilizing primary texts, including narratives, photographs, and maps, through which students explore the following question: "What motivated thousands of people to journey west during the 1800s?"