• photo of a replica keelboat with a crew member on the bow at sunset

    Lewis & Clark

    National Historic Trail ID,IL,IA,KS,MO,MT,NE,ND,OR,SD,WA

Environmental Factors

scenic view of mountains looking west from Rt. 275 between Three Forks and Helena, near Townsend, Montana

Looking west from Montana Rt. 275 between Three Forks and Helena, near Townsend, Montana.

NPS JH-Anderson

Many environmental factors exist along the Lewis and Clark National Historic Trail. Everything from non-native species to untimely releases of water from dams, to the loss of habitats, can have significant impacts to this historic corridor.




Learn about some of these factors by visiting sites along the trail highlighted in the right-hand column.

Did You Know?

William Clark's signature at Pompeys Pillar

Two hundred years after the Lewis and Clark Expedition, the only physical evidence of the journey is found near Billings, MT. In July 1805, William Clark carved his name into the soft rock of what he called Pompeys Tower. This site is now preserved at Pompeys Pillar National Monument.