Louisiana (New Spain) had been under Spanish possession sing the 1763 Treaty of Paris that ended the Seven Year’s War.
Then the Third Treaty of San Ildefonso (formally titled the Preliminary and Secret Treaty between the French Republic and His Catholic Majesty the King of Spain, Concerning the Aggrandizement of His Royal Highness the Infant Duke of Parma in Italy and the Retrocession of Louisiana) was a secretly negotiated treaty between France and Spain in which Spainish representatives officially returned the colonial territory of Louisiana to France.
The treaty was concluded on October 1, 1800 between Louis Alexandre Berthier representing France and Don Mariano Luis de Urquijo representing Charles IV of Spain.
The treaty was negotiated under some duress, as Spain was under pressure from Napoleon.
The terms of the treaty also did not specify the boundaries of the territory being returned, which later became a point of contention between Spain and the United States after the Louisiana Purchase.
This treaty also affirmed the earlier Treaty of Alliance signed at San Ildefonso on August 19, 1796.
The treaty agreement was kept top secret.
Treaty of Aranjuez of 1801
This additional treaty was signed on March 21, 1801, by Manuel Godoy and Lucien Bonaparte at Aranjuez. The conditions of this new treaty renewed those of the former ones, yet also expanded them.
This new agreement was signed by Charles IV of Spain on April 11, 1801.
Even though not written in the treaty, the French delegation had pledged to Spain that in case France wished to leave Louisiana, it only would be given back to Spain and not to any other state.
On October 15, 1802, Charles IV published a Royal Bill in Barcelona that made effective the transfer of Louisiana, providing the withdrawal of the Spanish troops in the territory, on condition that the presence of the clergy be maintained and the inhabitants keep their properties.
However, Napoleon first needed peace with Great Britain to implement the Treaty of San Ildefonso and take possession of Louisiana.
Otherwise, Louisiana would be an easy prey for Britain or even for the United States.
Thus, in fact, early in 1803, a continuing war between France and Britain seemed unavoidable.
On March 11, 1803, Napoleon even began preparing to invade Britain.
As history has uncovered, President Jefferson was prepared to pay up to $10 million for New Orleans and its environs, but were dumbfounded when the vastly larger territory was offered for $15 million.
Jefferson had authorized only the purchase of New Orleans.
The Americans thought that Napoleon might withdraw the offer at any time, preventing the United States from acquiring New Orleans, so they agreed and signed the Louisiana Purchase Treaty on April 30, 1803.
In fact the signed sale did not reach Washington D.C. until July 4, 1803.
Then finally on November 30, 1803, Spanish representatives officially returned the colonial territory of Louisiana to France.
Louisiana did not remain for long under French sovereignty as Napoleon Bonaparte had already secretly sold the territory to the United States, turning over possesion only 20 days later.
With this deal, Bonaparte and France dismissed its promise to Spain not to sell the territory.
The Louisiana Territory was in fact vast, stretching from the Gulf of Mexico in the south to Rupert’s Land in the north, and from the Mississippi River in the east to the Rocky Mountains in the west. Acquiring the territory actually doubled the size of the United States for a sum of less than 3 cents per acre.
Also worth noting is an interesting historical fact: Spain had refused Lewis and Clark permission to travel up the Missouri River, since the transfer from Spain to France and eventually to the United States had not been made official.
The top secret Louisiana Purchase between France and the United States meant that Lewis and Clark had to spend the winter of 1803-1804 in Illinois at Camp Dubois just outside of St. Louis.
Now WE know em