Pompeys Pillar National Monument

Pompeys Pillar is a sandstone butte about 120 feet high beside the Yellowstone River east of Billings, and on its side is the only physical evidence left by the Lewis and Clark Expedition along its route: William Clark's name and the date, July 25, 1806, carved into the rock. The 51-acre national monument, designated in January 2001 and run by the Bureau of Land Management with the Friends of Pompeys Pillar, is one of the smallest in the country.

Clark was leading part of the expedition down the Yellowstone on the return journey, with Sacagawea and her infant son Jean Baptiste Charbonneau, whom Clark nicknamed Pomp. He climbed the rock, wrote of having "a most extensive view in every direction", and named it Pompey's Tower; the present name dates from 1814. The rock was already a landmark long before: it carries Native petroglyphs, and archaeological evidence points to about 11,000 years of human activity in the area. Hundreds of later travellers and settlers carved their names too.

From the parking area it is about three-quarters of a mile to the pillar. A boardwalk of about 200 steps climbs it, with Clark's signature at the first landing about 100 steps up, and the view from the top over the river and farmland at the second. The interpretive centre, opened in 2006, covers Clark's journey, Native cultures and local wildlife, and holds paintings and sketches by J.K. Ralston; outside are a tipi, replica canoes and a homesteader's farm. A camera inside lets those who can't climb see the signature.

The 2026 season has ended. The BLM ran the site from 1 May to 30 September, gates open 8 am to 4 pm and closed Tuesdays. Through the winter the vehicle gates and interpretive centre are shut. Recreation.gov says the monument stays open year-round to walk-in visitors from dawn to dusk, so you can park outside the gate and walk the three-quarters of a mile in, but call 406-875-2400 first to check conditions. The walk in is exposed, so dress for the wind.

In season, standard vehicles pay $7, and America the Beautiful passes cover entry. Fees can be paid by cash or card at the booth (no checks) or online through Recreation.gov. The site is day-use only, with accessible paved walkways, picnic tables and restrooms at the interpretive centre.