At the turn of the 19th Century, Americans were moving further westward. Settlers had crossed the Appalachian Mountains and headed for parts known and unknown. Pioneers like Daniel Boone had blazed trails and roads, allowing families to travel to new places. Soon, the Northwest Territory and other places were bustling with Americans.

Everyone wanted more: more places to live, more livestock for their farms. The one thing that the United States Government wanted more of was land. And the Louisiana Territory had a lot of land.

Louisiana was owned by France, and New Orleans was a huge French settlement. Many Americans lived in and around New Orleans, and many American ships sailed back and forth on the river. The U.S. Government wanted to protect American shipping and settlements.

So President Thomas Jefferson sent Robert Livingston to France to buy New Orleans and the surrounding area. Napoleon, who was by this time effectively the dictator of France, refused. He was involved in wars in Europe and had dreams of a western empire as well.

After Napoleon's initial refusal, Jefferson sent James Monroe as well to France, in hopes of convincing Napoleon to reconsider. The French leader did more than that: He offered to sell all of the Louisiana Territory, more than 828,000 square miles! Livingston and Monroe quickly accepted and offered to pay $15 million. Both sides agreed, and the Louisiana Territory became American. The final transfer came in 1803.

Why did Napoleon change his mind? Things were going badly for him, and he needed the money. Why did Livingston and Monroe accept? They would have seen silly not to.

With one transaction, the size of the country doubled. The landscape of the United States and North America would be forever changed.

Such a large land had many Americans living in it, but the bulk of it was unknown to Americans. So Jefferson sent Meriwether Lewis and William Clark to explore it.