Other mistake: When Cloud Dancing and Daniel walk a wounded Sully to a clearing, we see a road with what looks like flattened black tents on either side, and Cloud Dancing tells them the Army must have attacked it; that's what is left of a reservation. When it's a modern transport road for everyday access, very poorly disguised as a reservation camp.
Factual error: When Mike is talking with Colleen about women 'Having It All' while raising children, she mentions Dorothy raising four children while running a ranch, when Dorothy mentioned in earlier episodes that she has two daughters and one son (Tommy, who appeared in a prior episode).
Answer: A Cooper was someone who made various things out of wood including wooden caskets and even barrels.