What territory did the United States buy from France in 1803?

Why this is the answer

In 1803 the United States bought the Louisiana Territory from France, a vast stretch of land between the Mississippi River and the Rocky Mountains. France needed money for its wars in Europe and sold it for 15 million dollars, the largest purchase of land in American history. The Louisiana Purchase doubled the size of the country and opened the way west; Thomas Jefferson was President at the time. Either official answer is accepted: the Louisiana Territory, or simply Louisiana. Memory hook: 1803, from France, and the country doubled.