Pompeys Pillar is a 150-foot (46 m) sandstone pillar from the late Cretaceous Hell Creek Formation next to the Yellowstone River. It has an abundance of Native American petroglyphs, as well as the signature of William Clark, who named the formation after Sacagawea's infant son.
Leash Laws: Most parks require dogs to be on a leash in some or all areas, however, some parks allow dogs off leash in certain locations, please consult the parks website before going off leash, Thank you!
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