They traveled the Missouri River.
So that they can find out what is in that area and what inhabitants live there.
the Missouri River
the Missouri River
the Missouri River
Lewis and Clark followed the Missouri river.
Lewis and Clark traveled on the Colorado River for their expedition.
Lewis and Clark explored Missouri River, and Columbia River.
Missouri (and Columbia)
Lewis and Clark found the Missouri River.
Lewis and Clark split up during their expedition and Lewis stayed near to the Missouri River and Clark went south through the fringes on Montana till he found the Yellowstone River, which was also a tributary of the Missouri river. Then Clark would follow Yellowstone River east to meet the Missouri River and the expedition would continue.
Missouri and Columbia rivers