Clark at Pompeys Pillar

While descending the Yellowstone River, Clark carved his name and the date into a sandstone pillar he named “Pompy’s Tower” after Jean Baptiste Charbonneau, Sacagawea’s toddler son.

“This rock I shall call Pompy’s Tower, after the young Shoshone boy. I marked my name and the day of the month & year.”

Clark’s inscription — “Wm Clark July 25 1806” — remains visible today and is the only physical evidence of the expedition still in its original location along the trail. The site is now Pompeys Pillar National Monument, managed by the Bureau of Land Management.

Clark described the pillar as 200 feet high and 400 paces in circumference, with “a most extensive view in every direction” from its summit.