The United States paid $15 million for the Louisiana Purchase in 1803.
The agreement transferred the Louisiana territory from France to the United States. Robert Livingston and James Monroe negotiated for the United States, while François Barbé-Marbois represented France. The treaty was signed in Paris on April 30, 1803, and publicly announced in the United States on July 4.
Thomas Jefferson had initially authorized negotiators to seek New Orleans and nearby land because control of the port was vital to western farmers and merchants. Napoleon Bonaparte instead offered the entire Louisiana territory, partly because France had abandoned plans to rebuild a North American empire and needed funds amid renewed conflict with Britain.
The purchase covered approximately 828,000 square miles and nearly doubled the area of the United States. The price is often remembered as a simple $15 million payment, although the United States financed the transaction through bonds and assumed certain French debts owed to American citizens.