The United States completed the Louisiana Purchase from France in 1803, nearly doubling its territory.
The agreement transferred approximately 828,000 square miles of land to the United States. The territory stretched from the Mississippi River to the Rocky Mountains and from the Gulf of Mexico toward the Canadian border. The purchase price was $15 million, including the assumption of certain claims against France.
President Thomas Jefferson wanted control of New Orleans because the port was crucial to farmers and merchants using the Mississippi River system. French leader Napoleon Bonaparte unexpectedly offered the entire Louisiana territory after plans to maintain a French presence in North America changed.
The treaty was signed in Paris on April 30, 1803, and the United States took formal possession later that year. The purchase did not instantly resolve every boundary question, and its meaning for Indigenous nations and slavery became major issues. Lewis and Clark’s expedition soon helped map and describe the acquired region.