Pompeys Pillar: Lewis and Clark's Historic "Graffiti" on the Yellowstone

On July 25, 1806, at the height of summer, the Corps of Discovery stopped by a curious stump of sandstone on the Yellowstone River.  It had many Native-American markings, including ancient petroglyphs of small figures.  Captain William Clark decided to add another layer of history to the rock, and carved his name and the date into the side.  Then he named it after the offspring of Sacagawea and Toussaint Charbonneau, a French trapper and Sacagawea's husband.

After, many early trappers and settlers carved their name into the rock as well; it now stands as a testament to nearly 11,000 years of human habitation and interaction.

What Clark and company didn't know was that the sandstone formation, which dated back to the Cretaceous, was special for other reasons as well.  According to Roadside Geology of Montana, it has since yielded "the bones and teeth of various dinosaurs, pterosaurs, crocodiles, lizards, snakes, turtles, frogs, salamanders, fish and mammals."  

Today, Pompeys Pillar is close to Billings, Montana's biggest city.  It has been designated a National Monument by the Bureau of Land Management.  At only 51 acres in size, it is one of the smallest National Monuments in the country.

Access to the boardwalk that leads to the top of the pillar is restricted at this time while BLM reassesses the sturdiness of some of the rock's outcroppings, and the on-site interpretative center is closed until Phase 3 of Montana's reopening, but the pillar itself and the adjacent BLM lands are currently open.