What was the name of the 1803 U.S. acquisition of a vast territory from France?

The 1803 U.S. acquisition of a vast territory from France was the Louisiana Purchase.

The agreement transferred approximately 828,000 square miles to the United States for $15 million, or about three cents per acre. The territory stretched west from the Mississippi River toward the Rocky Mountains and included land that later became part of 15 U.S. states and two Canadian provinces.

President Thomas Jefferson had initially sought control of New Orleans and navigation on the Mississippi River. French officials unexpectedly offered the entire Louisiana territory, and American negotiators Robert Livingston and James Monroe accepted the deal. The treaty was signed in Paris on April 30, 1803.

The purchase nearly doubled the size of the United States and encouraged later exploration and westward expansion. It is sometimes confused with the later Alaska Purchase, which transferred Alaska from Russia in 1867. The Louisiana Purchase also raised constitutional questions because the U.S. Constitution did not explicitly describe a process for acquiring foreign territory.