Conversation so far:
what can you tell me about the early history of blackfoot?
The Niitsitapi, also known as the Blackfoot or Blackfeet Indians, reside in the Great Plains of Montana and the Canadian provinces of Alberta and Saskatchewan.
when did they reside in the great plains?
By 1200.

Question: what else did they do in those years?
Self-contained rewrite: What else did the Blackfeet do in the years around 1200 besides reside in the great plains?