DAR marker commemorates the site's discovery and naming by Captain Clark of the Lewis and Clark Expedition, which includes his inscribed signature, believed to be the only such left by the Expedition. The DAR marker reads, "”Pompey’s Pillar. Discovered and named by Captain William Clark of the Lewis and Clark Expedition July 25, 1806. With Clark returning down the Yellowstone were: Pryor, Shannon, Bratton, Windsor, Hall, Shields, Gibson, Labiche, Chaboneau, Sacajawea and child, York the slave. In gratitude to Lewis and Clark, those intrepid leaders, to Sacajawea, their unerring guide, and to the Fidelity and Courage of all the company. This tablet is dedicated by Shining Mountain Chapter Daughters of the American Revolution, Billings, Montana May 24, 1928”