Pompeys Pillar National Monument
A Yellowstone River sandstone outcrop holds Indigenous petroglyphs, William Clark’s 1806 signature, an interpretive center, and a sweeping view above the valley.
Artwork inspired by E. S. Paxson
The Pillar was significant long before Clark. Crow people know it as Iishbiiammaache, and Indigenous markings record deep relationships with a strategic river crossing and overlook. Clark’s dated signature is rare physical evidence of the expedition, but it belongs within that longer record.
A boardwalk climbs roughly two hundred steps to the signature and summit; the visitor center and lower paths provide context first. Heat, wind, seasonal gate closures, and cultural-resource protection matter, and no visitor should add a mark to the stone.
- Clark signed
- July 25, 1806
- Height
- About 120 feet
- Allow
- 2–3 hours
Quick guide
- First question
- Place Clark’s 1806 signature within—not above—that history.
- Set beside it
- About 120 feet ↔ Place Clark’s 1806 signature within—not above—that history
A focused visit to Pompeys Pillar National Monument
- Begin
- Center Iishbiiammaache and the long Indigenous record before moving into the wider story.
- Then
- Place Clark’s 1806 signature within—not above—that history.
- Climb prepared
- Expect about two hundred steps to the summit.
- Protect
- Touch no petroglyph or inscription and add absolutely nothing.
Good to know
The monument gate and visitor center operate seasonally, and maintenance can occasionally close them midweek; daylight walk-in access may differ. Confirm hours, carry water, and know that the upper boardwalk is not wheelchair accessible.
Notice these
- July 25, 1806
- About 120 feet
- Place Clark’s 1806 signature within—not above—that history.