Spain's alliance with France and the 1798-1802 Anglo-Spanish War resulted in a British naval blockade that severely impacted their economy. This was highly dependent on trade with its South American colonies, particularly the import of silver from Mexico. Louisiana formed the North-Eastern border of Spain's immense Empire in the Americas, which it had acquired relatively recently in the 1763 Treaty of Paris. Possession led to constant battles over illegal American activity in the Mississippi Basin, which was both costly and risked conflict with the US, whose merchant ships Spain relied on to evade the British blockade. After the November 1799 Coup of 18 Brumaire, the new government of First Consul Napoleon and his deputy Talleyrand made colonial expansion a key policy. Part of this involved the creation of a new French Empire in North America, with Louisiana as its hub. This combination of French ambition and Spanish weakness made an exchange attractive to both, preliminary terms being agreed in the secret October 1800 Third Treaty of San Ildefonso. In return for Louisiana, Charles IV's son-in-law Louis, Infanta Duke of Parma would be compensated for France's annexation of his inheritance, the Duchy of Parma. Details were vague, Clause II stating 'it may consist of Tuscany...or the three Roman legations or of any other continental provinces of Italy which form a rounded state;' Spain would hand over Louisiana once this was confirmed.
This elaborate shuffling of Italian territories ultimately led nowhere; Etruria was dissolved and incorporated into France in 1807, while much of pre-Napoleonic Italy was restored by the Congress of Vienna in 1815, including the Grand Duchy of Tuscany and the Duchy of Parma. Negotiations between France and Britain to end the War of the Second Coalition began in late 1801, resulting in the March 1802 Treaty of Amiens which brought temporary peace to Europe. In December 1801, a French army landed on the West Indian island of Saint-Domingue, which had become effectively self-governing under the rule of Toussaint Louverture; bringing it back into submission would be the first step in re-creating France's American empire. Between 1798–1800, the United States and France fought an undeclared war at sea known as the Quasi-War, which was ended by the September 1800 Convention of 1800 or Treaty of Mortefontaine. French ambitions in North America concerned the United States; with Britain to the north in Canada, the US government much preferred a weak Spain to an aggressive and powerful France on its southern border. They were also aware France had conducted military surveys of Louisiana, including the Ohio and Mississippi valleys, to determine how best to defend it against US expansion if they regained control. French ambitions seemed clear and the presence of over 30,000 veteran troops in Saint-Domingue meant they could enforce that policy. The US Ambassador to Spain, Charles Pinckney, was instructed to acquire Louisiana and the Floridas from the Spanish if possible but they denied any such deal had been agreed. It was not until February 1802 the Americans finally obtained details of the Treaty of Aranjuez from Rufus King, their envoy in London. However, by late 1802 it was becoming apparent that the Saint-Domingue expedition would likely end in failure, with Napoleon's brother-in-law, General Charles Leclerc dying from yellow fever along with many of his troops.. If Saint-Domingue were not brought back under French command, Louisiana would become much less relevant to France. With war against Great Britain likely to resume, Napoleon considered the possibility of selling the territory. Although France had pledged in the agreement with Spain not to transfer Louisiana to any other country, it sold the territory to the United States for $15 million in April 1803, one month before the resumption of war with the British.
