Between 1800 and 1801, Spain secretly returned the Louisiana Territory to French custody; Spain was ceded the Territory in the 1763 Treaty of Paris, treaty which ended the Seven Year’s War. Napoleon planned to use the Territory as his North American imperial sear.
The United States government learned of this in 1802. The knowledge caused no small amount of panic. The government which controlled the Louisiana Territory controlled the mouth of the Mississippi River in New Orleans, and whomever controlled the mouth of the Mississippi controlled the economy of the North American continent. And indeed, the Unites States’ government’s fears came true when Napoleon closed the New Orleans port.
Map of the Louisiana Purchase; courtesy of A People and a Nation: Volume I Ninth Edition by Mary Beth Norton
But something was happening in the background of all of this which would permanently destroy Napoleon’s plans, and alter the future of the United States.
The slave revolt of St. Domingue began in 1791. It came to a close in 1804, with the complete overthrow of French colonial rule. Today, this is known today as the Haitian Revolution.
Napoleon planned to use St. Domingue as his Caribbean base from which to launch his new empire, with its enslaved labor force and the revenue he gained its work as the backbone of the infrastructure of this new empire.
Having lost that holding, that labor force, and all the money that came with it, Napoleon had to scarp his imperial plans. The Louisiana Territory no longer financially tenable for France, Napoleon sold it to the United States in 1803; Thomas Jefferson purchased it for $15 million, $233 million in today’s money. This was the Louisiana Purchase.
And just an interesting note about the Haitian Revolution: the use of the same philosophies which inspired the American Revolution by a black, enslaved population terrified people like Thomas Jefferson so much that they could barely speak of it; they had no idea how to make sense of it within their precisely constructed idea of race. So they just kind of ignored it and began and enacted a policy of brutal expansion throughout the Louisiana Purchase.