Third Treaty of San Ildefonso

The Third Treaty of San Ildefonso, secretly negotiated and signed by French minister Louis Alexandre Berthier and Spanish secretary of state Don Mariano Luis de Urquijo at the Spanish royal residence near San Ildefonso on 1 October 1800, provided for the return of the Louisiana Territory from Spain to France. The Treaty of Aranjuez, on 21 March 1801, and a final agreement of retrocession signed by Carlos IV, king of Spain, on 15 October 1802 completed the transfer. The treaty and events that followed it had significant consequences for Mississippi.

The French effort to recover Louisiana started in 1795 but gained momentum in 1799 with the emergence of Napoleon Bonaparte, who envisioned an American empire anchored by sugar-rich Saint-Domingue (present-day Haiti). In September 1800 Berthier presented Spain with a French ultimatum demanding the transfer of Louisiana, East and West Florida, and ten ships of war. With Spain’s fragile control of Louisiana weakened further by the 1795 Treaty of San Lorenzo, in which Spain recognized the western and southern boundaries of the United States as the Mississippi River and the thirty-first parallel, respectively, Carlos IV agreed to give France Louisiana and six ships of war but refused to surrender the Floridas. In exchange, the king received a throne for his son-in-law, the Duke of Parma in Italy.

Pres. Thomas Jefferson’s administration heard rumors of the Third Treaty of San Ildefonso and received a copy from Rufus King, American minister to Great Britain, in November 1801. Jefferson directed Robert R. Livingston, American minister to France, to determine the status of Louisiana and offer to buy New Orleans. Although the French minister, Talleyrand, spurned Livingston’s initial efforts, a slave insurrection in Saint-Domingue and the specter of war in Europe caused Napoleon to scrap his plans for an American empire. Jefferson pushed the negotiations in Paris and authorized additional military preparations along the Mississippi River after Spanish intendant Juan Ventura Morales suspended the right of deposit at New Orleans in October 1802. James Monroe joined Livingston in Paris on 10 April 1803, and negotiations with the French treasury minister, François Barbé-Marbois, soon concluded with an agreement to transfer Louisiana to the United States for $15,000,000.

The unexpected consequences of the Third Treaty of San Ildefonso allowed the American ministers to acquire not just New Orleans or some territory for a port on the Mississippi, as Jefferson had authorized, but a vast, boundless empire west of the Mississippi. The final cession agreement on 30 April 1803 included a treaty and two financial conventions in which the United States paid France $11,250,000 and settled claims by American citizens against France amounting to $3,750,000. Despite protests from Spain and the Federalists, the US Senate ratified the Louisiana Purchase on 17 October 1803. US commissioners William C. C. Claiborne and James Wilkinson formally accepted the transfer on 20 December, following a similar ceremony on 30 November when the Spanish commissioner officially delivered Louisiana to the French prefect, Pierre Clément Lausset. Claiborne left his position as governor of Mississippi Territory to become governor of the Territory of Orleans and served as governor of Louisiana following its admission to statehood in 1812.

Further Reading

  • Mary P. Adams, Journal of Southern History (May 1955)
  • David B. Gaspar and David Patrick Geggus, eds., A Turbulent Time: The French Revolution and the Greater Caribbean (1997)
  • Lawrence S. Kaplan, Thomas Jefferson: Westward the Course of Empire (1998)
  • James E. Lewis Jr., The American Union and the Problem of Neighborhood: The United States and the Collapse of the Spanish Empire, 1783–1829 (1998)
  • Treaty of San Ildefonso, Avalon Project, Yale Law School website,
  • Daniel J. Weber, The Spanish Frontier in North America (1992)

Citation Information

The following information is provided for citations.

  • Article Title Third Treaty of San Ildefonso
  • Author
  • Keywords Third Treaty of San Ildefonso
  • Website Name Mississippi Encyclopedia
  • URL
  • Access Date July 6, 2020
  • Publisher Center for Study of Southern Culture
  • Original Published Date
  • Date of Last Update April 15, 2018