Pompeys Pillar is a unique geological formation born of water. Sediments carried by an ancient river were very slowly and forcefully compacted into rock, the same sandstone and siltstone visible today in the Pillar. As the waters receded and sediment eroded, this pillar of rock was left standing alone and isolated on the south side of the Yellowstone River. Wind, rain, freezing, and thawing are natural processes that have been reshaping the Pillar for thousands of years. Today, erosion has accelerated swiftly and now requires stabilization of portions of the rock, including the area containing William Clark's signature. To help Pompeys Pillar survive for future generations, geotechnical engineers will assess conditions and make recommendations before work begins on shoring up the stone bones of Pompeys Pillar. Even without climbing the rock, people can still experience the natural wonder that captivated William Clark and has attracted human activity for millennia by walking around its base, exploring it from the point of view of Clark's arrival, watching wildlife, walking along the Yellowstone River, and hiking nearby nature trails.