Louisiana Purchase

wars, France lost all of its possessions in North America removing hopes of a colonial empire.
In 1801, Spain signed a secret treaty with France to return Louisiana Territory to France.
Since the late 1780s, Americans had been moving westward into the Ohio River and Tennessee River valleys, and they were highly dependent on free access to the Mississippi River and the strategic port of New Orleans.
U.S. officials feared that France, under the leadership of Napoleon Bonaparte, would soon seek to dominate the Mississippi River and access to the Gulf of Mexico.

the right to store goods in New Orleans.
1803 - Jefferson sent James Monroe to Paris to aid Livingston in the New Orleans purchase talks.
France offers Louisiana for sale to the United States.

WHY?

the failure to put down a slave revolution in Haiti
the impending war with Great Britain
probable British naval blockade of France
financial difficulties

agreed to pay $11,250,000 and assume claims of American citizens against France in the amount of $3,750,000.
In exchange, the United States acquired the vast domain of Louisiana Territory, some 828,000 square miles of land.