Final answer:
The Louisiana Purchase was significant because it doubled the size of the U.S., provided control over New Orleans for trade, and impacted the national discussion on slavery. It also encouraged exploration and represented a diplomatic success for the Jefferson administration.
Step-by-step explanation:
The Louisiana Purchase was a pivotal moment in American history that significantly influenced the nation's economic and political landscape. One of its primary importance was that it gave the United States control of the port of New Orleans and a vast territory that doubled the size of the country. Control of the Mississippi River and the port of New Orleans was crucial for trade and westward expansion. Through this acquisition, the United States gained valuable land for agriculture, which was significant to Thomas Jefferson's vision of an agrarian republic. It also had a substantial impact on the balance between free and slave states and prompted discussions on the spread of slavery into new territories.
The Louisiana Purchase also marked a significant territorial achievement, as it provided an impetus for exploration, notably the Lewis and Clark expedition, which sought to discover trade routes and map the newly acquired territory. Lastly, it marked a critical strategic diplomacy win for the Jefferson administration, as it was acquired from Napoleon for a relatively small amount, adding considerably to the U.S. territory without resorting to war.