Treaty of San Ildefonso

The Treaty of San Ildefonso, signed in 1800, was an agreement between Spain and France. It resulted in Spain transferring the Louisiana Territory, which included land west of the Mississippi River, back to France. This treaty was part of a larger plan by France to strengthen its empire in North America and set the stage for Napoleon's later efforts to sell the land to the United States in the Louisiana Purchase of 1803. The treaty was kept secret at first, revealing the shifting alliances and colonial ambitions of European powers at the time.