In July 1806, William Clark (of the Lewis and Clark Expedition) passed through the Billings area. On July 25 he arrived at what is now known as Pompey's Pillar and wrote in his journal "... at 4 P M arrived at a remarkable rock, i ascended this rock and from its top had a most extensive view in every direction." Clark carved his name and the date into the rock, leaving the only remaining physical evidence of their expedition. He named the place Pompey's Tower, naming it after the son of his Shoshone interpreter and guide Sacajawea. In 1965, Pompey's Pillar was designated as a national historic landmark, and was proclaimed a national monument in January 2001. An interpretive center has been built next to the monument.
