For roughly 4 cents an acre, the fledgling United States doubled in size with the Louisiana Purchase Treaty, signed 210 years ago with France on April 30, 1803.
Acting on orders from President Thomas Jefferson (who had put his doubts as to the constitutionality of the expansion aside) American agents James Monroe and Robert Livingston had planned only to negotiate for the purchase of New Orleans and Florida from France. Instead they were offered the entire territory for the equivalent of 15 million dollars, an offer they hastily accepted.
October 20, 1803 - When Thomas Jefferson’s envoys agreed to purchase Louisiana Territory from France on April 30, 1803, they did so without his direct approval. While Jefferson debated the constitutionality of the acquisition, French ruler Napoleon Bonaparte become impatient and threatened to void the treaty. Jefferson was forced to push for ratification, and received the consent of the Senate on October 20 by a vote of twenty-four to seven. The next day in Washington, the Americans and the French envoy exchanged ratified copies of the treaty.
Senate resolution of advice and consent to Louisiana Purchase Treaty, 10/20/1803; General Records of the U.S. Government