Allegorical illustration depicting the sale of Louisiana by Napoleon I to the United States for 15 million of dollars. Two years earlier, Spain had ceded it to France on condition that it would be returned if the French government would part with it. France sold it without respecting the treaty with Spain.In December 1803 France transferred authority over the region to the United States. Engraving by Chamorro. Historia del Levantamiento, guerra y revolucion de Espana by the Conde de Toreno. Madrid, 1851. (Photo by: Prisma/Universal Images Group via Getty Images)