Question: Laton Alton Huffman was an American photographer who worked at an Army post  situated on the south bank of the Yellowstone River, at the mouth of what?
Sentence (from "Nez Perce in Yellowstone Park"): Eventually, the army's pursuit forced the Nez Perce off the Yellowstone plateau and into forces arrayed to capture or destroy them when they emerged from the mountains of Yellowstone onto the valley of the Yellowstone River.
Relevant evidence: No