The "Secret Treaty of Ildefonso" and Napoleon: A Historical Correction

There was no "Secret Treaty of Ildefonso" between Spain and Napoleon. The question likely confuses several agreements:

Actual Treaties

• Treaty of San Ildefonso (1796): Spain allied with France against Britain
• Treaty of San Ildefonso (1800): Spain secretly retroceded Louisiana to France (Third Treaty of San Ildefonso)
• Treaty of Fontainebleau (1807): Spain allowed French troops to cross to invade Portugal; secret clauses partitioned Portugal
• Napoleon's Forgery (1807): Napoleon fabricated a "Treaty of Ildefonso" ceding Portuguese Louisiana/Florida to France to justify his actions

What Spain "Returned" to France (1800)

Under the Third Treaty of San Ildefonso (1800), Spain returned Louisiana (the vast territory west of the Mississippi) to France—which Napoleon then sold to the US in 1803 (Louisiana Purchase). Florida was not included (Spain kept East/West Florida until 1819/1821).

The forged 1807 document is a historical curiosity, not a real treaty.