What was the name of the 1803 agreement that transferred Louisiana to the United States?

The 1803 agreement that transferred Louisiana to the United States was the Louisiana Purchase.

The purchase treaty was signed in Paris on April 30, 1803, by Robert Livingston and James Monroe for the United States and François Barbé-Marbois for France. It transferred the Louisiana Territory for $15 million, a sum that included the assumption of certain American claims against France.

The acquisition extended from the Mississippi River toward the Rocky Mountains and from the Gulf of Mexico northward. Because the territory’s boundaries were not perfectly defined, disputes with Spain continued after the purchase.

The Louisiana Purchase is sometimes confused with the Adams–Onís Treaty of 1819. That later agreement settled borders with Spain and transferred Florida to the United States. The Louisiana treaty itself was a purchase from France, not a conquest or a Spanish cession.