• 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.

  • Results of springtime melt on Knife River Results of springtime melt on Knife River

    Flooding of the Knife River threatens archeological sites. Read More

  • River otters need good water quality to survive River otters need good water quality to survive

    A Water Quality Baseline Inventory is used by scientists and researchers. Read More

  • Aerial view of James River Islands on the Missouri Aerial view of James River Islands on the Missouri

    Missouri National Recreational River presents factors that threaten the river's ecology and beauty. Read More

  • Rolling hills from Nez Perce visitor's center Rolling hills from Nez Perce visitor's center

    Since the arrival of man, the vegetation communities of the Plateau have experienced change. Read More

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.