Question

Lewis and Clark's exploration of the Missouri River was very important for the westward expansion of the United States. For example, the information they gained
A.
allowed the river to become a major transportation route for settlers of the Great Plains.
B.
allowed the river to become a major transportation route for the Army during the Mexican War.
C.
prevented the Native American tribes of the Rocky Mountains from harassing American settlers.
D.
prevented the British from expanding their settlements from the Pacific Northwest eastward.

Answer 1

D. The expedition strengthened U.S. claims to the Oregon Country and demonstrated American interest and presence in the Pacific Northwest, helping to check further British expansion eastward.