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.
PBS
Pbs: Lewis and Clark: Yankton Sioux Indians
Read about what the Yankton Sioux wanted from Lewis and Clark and why they were disappointed when they met the Corps of Discovery on its journey up the Missouri River. From PBS.
PBS
Pbs: Yankton Sioux Indians
Provides information on the Yankton Sioux Indians and the Lewis and Clark expedition.