The summer of 1806 found Lewis and Clark’s Corps of Discovery on their return trip from the Pacific Ocean to St. Louis. Led by Meriwether Lewis and William Clark, the band of explorers, which initially consisted of some 55 people, had traveled from St. Louis, Missouri to the Pacific Ocean. President Jefferson had tasked them to find a viable water route to the Pacific Coast. Moreover, they discovered 178 new plants species and 122 animal species. They charted and mapped the rivers and mountains of the plains and Rockies and established friendly relations with many Native American tribes.
On June 30, 1806, the Corps were returning home when they decided to make a brief stop at a meadow along the Bitterroot River known as Traveler’s Rest. During that stay, Lewis and Clark determined to divide their forces into different groups so that they could explore as much territory as possible. Clark and Sacagawea, a Shoshone woman, led their party through the Bozeman Pass. They constructed cottonwood log canoes to float down the Yellowstone River. After floating for several days, Clark spotted an enormous rock structure on July 25 and decided to stop and climb it. In his journal Clark recorded, “At 4PM [I] arrived at the remarkable rock situated in an extensive bottom. This rock I ascended and from it's top had a most extensive view in every direction. This rock which I shall call Pompy's Tower is 200 feet high and 400 paces in secumpherance and only axcessible on one side which is from the N.E. the other parts of it being a perpendicular clift of lightish coloured gritty rock.The Indians have made 2 piles of stone on the top of this tower. The nativs have ingraved on the face of this rock the figures of animals &c.”
Clark named the large sandstone rock Pompys Tower after Sacagawea’s son Jean Baptiste Charbonneau, who Clark nicknamed “Pomp” and who would eventually become Clark’s adopted son. Clark also carved his now famous inscription on the pillar, including his name and the date, July 25, 1806. This mark is one of the few visible remnants of expedition along the Lewis and Clark National Historic Trail.