About Pompeys Pillar
A solitary sandstone mass rises beside the Yellowstone River, carrying a rare, tangible mark from the Lewis and Clark expedition. On July 25, 1806, William Clark climbed the rock and carved his name and the date. The signature remains visible from a boardwalk, alongside other markings that reflect the site’s much longer human history.
The pillar stands about 120 feet high. A boardwalk with roughly 200 steps reaches the upper viewing area, while a visitor center explains Clark’s route, Native cultures, and the surrounding river landscape. The rock itself is protected; visitors see the inscription without approaching the fragile surface.
For the 2026 season, the monument’s staffed gates are open through September 30, with Tuesday closures for maintenance; daylight walk-in access is possible when vehicle gates are shut. A standard vehicle carrying one to six people pays $7, and America the Beautiful passes are accepted. Check the BLM page for current access before driving out.