July 27th
Clark Days are held at Pompeys Pillar each year on the last weekend of July. The event commemorates William Clark's stop at the site on July 25, 1806, on his trip down the Yellowstone River. Activities include interpretive programs, demonstrations, nature walks, and a main presentation. The Saturday night of Clark Days is the only night of the year when overnight camping is allowed at the Pillar. The Bureau of Land Management has park rangers on duty at the visitor center to assist campers.