The Lewis and Clark expedition (1803–1806) was important because it (1) determined the route of the first transcontinental railroad (2) opened an all-water route to the Gulf of Mexico (3) removed the British threat from the Northwest Territory (4) increased understanding of the area included in the Louisiana Purchase
The Lewis and Clark expedition (1803–1806) was important because it "(4) increased understanding of the area included in the Louisiana Purchase," since the US had recently purchased this new territory.
