On their return trip, Lewis and Clark separated at Travelers' Rest near present day Missoula to be able to explore more territory. The Lewis party took the "Road to the Buffalo" which led them to the Great Falls of the Missouri and exploration of the Marias River. The Clark party was to explore the Yellowstone River. There Clark came upon a large sandstone formation which he named for Sacajawea's son Jean Baptiste. Clark had given the boy the nickname Pomp which means "little chief" in Shoshoni. At Pomp's Tower Clark carved his signature leaving the only physical evidence of the Lewis and Clark Expedition. A later biographer edited his journal to read Pompeys Pillar.