Napoleon sold it to the United States for pennies per acre, and ended the period of French Colonialism in the midwestern portion of the landmass we now call the continental United States of America.
The Louisiana Purchase was the acquisition by the United States of 828,000 square miles (2,140,000 km²) of French territory ("Louisiana") in 1803. The cost was 60 million francs ($11,250,000) plus cancellation of debts worth 18 million francs ($3,750,000). Including interest, the U.S. finally paid $23,213,568 for the Louisiana territory. Not a bad deal.
We got the port of New Orleans as well as the navigation 'rights' on the Mississippi River and Missouri Rivers. It opened up a vast region that encompasses the current region of 15 states, which comprises around 23% of the territory of the United States today.