On May 2, 1803, a treaty was signed selling the Louisiana Territory to the United States for $15 million.
The western half of the Mississippi River Basin — 530,000,000 acres over 828,000 square miles — was purchased from France by the United States at less than 3 cents per acre, leading some to describe the transaction as “the greatest land bargain in U.S.history.”
According to the Encyclopedia Britannica France had ceded Louisiana west of the Mississippi River to Spain in 1762. But when Napoleon Bonaparte took control of France, he convinced King Charles IV of Spain to give Louisiana back to France in 1801. The agreement was known as the Treaty of San Ildefonso.
Through the Pinckney Treaty of 1795, Spain had allowed the United States to use the Mississippi River for transportation and for settlers to export their goods from New Orleans without paying a duty or for temporary storage.
U.S. President Thomas Jefferson was concerned that the control of Louisiana by France was not good for the United States, and wanted to at least purchase New Orleans for economic and national security reasons.
Jefferson sent his U.S. minister in Paris, Robert R. Livingston, to negotiate a possible deal with France’s counterpart, but the negotiations initially fizzled. Livingston’s signals of a closer alliance with Great Britain, French losses in Saint-Domingue and the need for money to supply Napoleon’s military efforts eventually pushed the French leader to sell the entire Louisiana Territory to the United States.
A treaty was signed on May 2, but was back-dated to April 30 for official reasons, selling the Louisiana Territory to the United States in the form that France had received it from Spain. The United States Senate approved the treaty by a vote of 24 to 7. After interest payments, the final settlement was $27,267,622.
The Louisiana Purchase doubled the size of the United States. The land was valuable and contained rich mineral resources and wildlife resources. It was eventually carved into several states — Louisiana, Missouri, Arkansas, Iowa, North Dakota, South Dakota, Nebraska, and Oklahoma. The territory also included some land in Kansas, Colorado, Wyoming, Montana and Minnesota.