Pompeys Pillar National Monument protects a sandstone butte above the Yellowstone River, best known for William Clark's 1806 signature carved during the Lewis and Clark expedition. The mark is small, but the setting gives it weight: river, cottonwoods, cliffs, and open plains all meet here.
Climb the steps for the view and spend time in the interpretive center before or after. The monument works because it ties one famous expedition note to a much older travel corridor used by Indigenous peoples, wildlife, traders, and later settlers.