Clark marked his presence by engraving his name and the date of his visit on the outcrop. This simple inscription is the only remaining on-site physical evidence of Lewis and Clark's epic journey.

Clark named this rock Pompy's Tower. It was renamed Pompeys Pillar in 1814 when the Lewis and Clark journals were published. Pompy was Clark's nickname for young Jean Baptiste Charbonneau whose mother, Sacagawe, was the party's interpreter. Pomp means "little chief" in the Shoshoni language.

Popmpey Pillar is a massive sandstone outcrop that rises 150 feet from a two-acre base on the banks of the Yellowstone River. The location at a natural ford in the river, and its geologic distinction as the area's only major sandstone formation on the south side of the river, have made Pompeys Pillar a celebrated landmark and outstanding observation point for more than 11,000 years.

Hundred of markings, petroglyphs, and inscriptions left by visitors have transformed this geologic phenomenon into a living journal of the American West. Ethnographic and archaelogical evidence indicates that the Pillar was a place of ritural and religious activity. Hundreds of petroglyphs on the face of the rock reflect the importance of the monument to early peoples.

Row 1--#4-Row 2--#1-Clark's suthograph, #2-4-other autographs. Row 3--#4-view from top across river, same as display picture, #5-up river, Row 3--#1-down river, #4-2 dugout canoes lashed together which allowed them to carry more equipment with fewer men.