Pompeys Pillar - Pompeys Pillar National Historic Landmark, MT. Clark and his party arrived at a large sandstone rock formation on July 25, 1806. He named it "Pompey's Tower" after Sacagawea's son, Jean Baptiste Charbonneau. Clark had developed a great fondness for the boy and had given him the nickname, "Pomp." In the Shoshone language, "Pompy" means "Little Chief."
