Clark's signature and date, July 25, 1806 is inscribed
on the wall. Clark wrote that he climbed the sandstone pillar and "had a most
extensive view in every direction on the Northerly Side of the river". He named
the outcropping after Jean Baptiste Charbonneau—the son of expedition member
Sacagawea—whom he nicknamed "Pompey". His original name for it was "Pompey's
Tower"; it was changed to the current title in 1814.