What did the Louisiana Purchase do?

The Louisiana Purchase is know for being one of the greatest land sale bargains in United States history.
In 1803, the United States purchased 828,000 square miles from France. The United States paid France fifty million francs ($11,250,000 USD) and a cancellation of debts worth eighteen million francs ($3,750,000 USD). This totaled sixty-eight million francs, or about $15,000,000 USD—equaling a purchase of less than three cents per acre.
This purchase nearly doubled the size of the United States, adding land of fifteen present U.S states as well as land to two present Canadian provinces. While then President Thomas Jefferson of the United States originally sought to only purchase the city of New Orleans and some adjacent coastal lands of Louisiana at the time, he later accepted the bargain of purchasing more land so that the United States could expand into a larger nation.
Prior to the Louisiana Purchase, it was unclear as to whether the United States Constitution authorized the purchase of land from other countries. Based on Jefferson’s decision, it is implied that the federal government holds the power to purchase territory through the negotiation of United States treaties. Before the Louisiana Purchase, federalists argued that purchasing land from other nations was unconstitutional because the constitution does not specifically authorize the federal government to make land purchases from other nations.

The Louisiana Purchase of 1803 involved the US government buying almost 820,000 square miles of land from France, doubling the size of the country. The purchase greatly expanded the territorial boundaries of the United States, stretching from the Mississippi River in the east to the Rocky Mountains in the west, and from the Gulf of Mexico in the south to the United States's northern border with Canada. Eventually, some fifteen states were created out of the new territory, representing arguably the greatest single achievement of Thomas Jefferson's presidency. At $15 million—or less than three cents an acre—the Louisiana Purchase represented quite a bargain for the United States. Napoleon was keen to sell the land as he was getting tied down in various foreign engagements, and French landholdings in North America were proving to be an expensive burden that merely added to the country's economic woes.
https://www.monticello.org/thomas-jefferson/louisiana-lewis-clark/the-louisiana-purchase/