Conversation so far:
What were the purposes of the Lewis and Clark expedition?
Their mission was to explore the unknown territory, establish trade with the Natives and affirm the sovereignty of the United States in the region.
What were important plants and animals Lewis and Clark discovered?
Black greasewood (Sarcobatus vermiculatus)Blue flax (Linum lewisii)Buffaloberry (Shepherdia argentea)Curly-top gumweed (Grindelia squarrosa)Fringed sagebrush (Artemisia ludoviciana)Indian tobacco (Nicotiana quadrivalvis)Lanceleaf sage (Salvia reflexa)Shadscale (Atriplex canescens)
What were the diplomatic objectives of the Lewis and Clark expedition?
Their mission was to explore the unknown territory, establish trade with the Natives and affirm the sovereignty of the United States in the region.

Question: What were the Native American tribes that they encountered
Self-contained rewrite: What were the Native American tribes that Lewis and Clark encountered?