In 1803, President Jefferson and a future president, Secretary of State James Madison, sent another future president, James Monroe, to join the US Minister to France, Robert Livingston, to facilitate real estate negotiations with France, but not quite the deal that ultimately happened. "Monroe's charge was to obtain land east of the Mississippi," wrote Gaye Wilson in "Jefferson's Big Deal: the Louisiana Purchase" in the Spring 2003 issue of the Monticello Newsletter. "Monroe's instructions, drawn up by Madison and approved by Jefferson, allocated up to $10 million for the purchase of New Orleans and all or part of the Floridas. If this bid failed, Monroe was instructed to try to purchase just New Orleans, or, at the very least, secure U.S. access to the Mississippi and the port.
"France's minister of finance, Francois de Barbé-Marbois, who had always doubted Louisiana's worth, counseled Napoleon that Louisiana would be less valuable without Saint Domingue [Haiti] and, in the event of war, the territory would likely be taken by the British from Canada. France could not afford to send forces to occupy the entire Mississippi Valley, so why not abandon the idea of empire in America and sell the territory to the United States?
"Napoleon agreed. On April 11, Foreign Minister Charles Maurice de Talleyrand told Livingston that France was willing to sell all of Louisiana. Livingston informed Monroe upon his arrival the next day."
It wasn't until the spring of 1804 that a ceremony (pictured above) marking the changes of sovereignty occurred upriver from New Orleans, where such ceremonies had been held in late 1803. Spain had agreed to turn Louisiana over to France in 1800, but it wasn't generally known, so the Spanish flag still flew over St. Louis until 1804. In a ceremony on March 9, that flag was lowered and the French flag was raised and allowed to fly until the morning of the 10th, when the US flag was raised. The Three Flags ceremony has been re-created in St. Louis a number of times since then, most recently for the bicentennial of the event in 2004.