Final answer:
The Louisiana Purchase roughly doubled the size of the United States, adding about 828,000 square miles of territory. For $15 million, a bargain at the time, the purchase secured crucial trade routes through the Mississippi River and New Orleans, though it raised constitutional and sectional issues.
Step-by-step explanation:
The Louisiana Purchase was an enormous acquisition for the United States, one which effectively doubled the size of the country. The territory itself was approximately 828,000 square miles. Claimed initially by Spain and later ceded to France, this vast expanse of land offered the United States control over the Mississippi River and New Orleans, both of which were critical for trade and westward expansion. Despite concerns over constitutional authority for such a purchase, President Thomas Jefferson, valuing agrarian expansion and the flood of farmable land, proceeded with the purchase in 1803. The transaction involved the exchange of $15 million, which was viewed as a bargain price for the amount of territory acquired, and ultimately shaped the future of the nation, including increasing debates over slavery in new territories.