Question: Which one of the two landmarks between which Rocky Mountain Trench stretches that is a large natural freshwater lake west of the Mississippi River?
Sentence (from "Flathead Lake"): Flathead Lake (Salish: člq̓etkʷ ) is the largest natural freshwater lake by surface area that is west of the Mississippi River in the contiguous United States, if one takes Red Lake and Lake of the Woods to be north of the Mississippi River, rather than west of the river.
Relevant evidence: Yes