The territory acquired by the United States in the Louisiana Purchase was a vast expanse of land that encompassed approximately 828,000 square miles. This acquisition, completed in 1803, doubled the size of the United States and included parts of 15 current states, stretching from the Mississippi River to the Rocky Mountains. The purchase was made from France, under Napoleon Bonaparte, and significantly facilitated Westward expansion, promoting economic growth, exploration, and settlement, while also stirring debates over slavery in the new territories.