The Louisiana Purchase was a land purchase made by United States president, Thomas Jefferson, in 1803. He bought the Louisiana territory from France, which was being led by Napoleon Bonaparte at the time, for 15 million USD. First, the men sent to France were allowed to spend up to 10 million USD in order to buy New Orleans and, if possible, the west bank of the Mississippi River. But then the French government said that for 5 million more dollars they would sell all of the Louisiana territory. Thomas Jefferson approved the deal and used his constitutional power to sign treaties to buy the land.
Napoleon Bonaparte sold the land because he needed money for the Great French War. The British had re-entered the war and France was losing the Haitian Revolution and could not defend Louisiana. Thomas Jefferson took the French offer as an opportunity to make America larger, even if it meant going against his Republican principles of small government (some would say he exceeded his constitutional power by accepting the deal on his own).
The Lewis and Clark expedition explored the Louisiana Purchase and the Oregon Territory. They started from St. Louis. Their route traced the Missouri River.
Adapted from: Louisiana Purchase Facts for Kids. Kiddle Encyclopedia.