What was the purpose of the Louisiana purchase?
The purpose of the Louisiana Purchase was to give the United States the port of New Orleans and thus control of the Mississippi river. Any other power in control of New Orleans would have been a natural enemy of the US because it could choke off all commerce from the western slopes of the Alleghenies, which went by river boat and flat boat to New Orleans and from there to the East Coast and the rest of the world.
As it turned out, the Purchase also nearly doubled the size of the United States and this side effect, thought to be a waste at the time, may have been the primary long-term benefit of the transaction.
The purpose of the exploration of the Louisiana Purchase, also known as the Lewis and Clark Expedition, was to find a water or land path to the Pacific. Other reasons were to reinforce the American claims to the territory, to gather information about the natives in the territory, and to gather information on resources in the area.