Marias River flows east, under I-15, top left, and continues toward the Missouri, left. Lewis camped farther east on the Marias 7/18 after a 24mi trek. He was a few miles above his 1805, spot, see lct64f. On the 19th they made 20mi along the north Marias bank; 7/20's march ended 28mi later on the north side of Marias, 5+/- mi southwest of Shelby MT. a bit west of I-15. Top left photo is the approximate area of the river for the camp. Top right, the Marias' source; Two Medicine River, left, Cut Bank Creek on the right.