"The mission is located upon a hill overlooking extensive prairies stretching to the east and west toward the Coeur D'Alene Mountains and the Columbia River. About a hundred acres of the eastern prairie adjoining the Mission are enclosed and...
"This valley for the most part is wide and open." There are "spurs separating it from the Hell-Gate Valley on the south," and "separate on the north the various tributaries flowing into the Blackfoot River." Plate LXII.
Approximately "fifty miles long and fifteen miles wide," Big Hole Prairie "is hemmed in by high mountains on every side except the southeast where Wisdom River passes out from it." Plate XLIX.
Lieutenant Mullan's party leaving the Bitter Root Valley and heading "down the river to the Lou-Lou Fork, which is fifteen yards wide and two feet deep at its mouth. Its valley is five hundred yards wide, and the mountains on each side are...