Why did Thomas Jefferson offer to buy Louisiana from France?

In 1800, under the leadership of Napoleon Bonaparte, France had successfully reclaimed a large swath of land from Spain in the Treaty of San Ildefonso. France had previously possessed the land but lost it to Spain during the tumultuous period prior to Napoleon. Once France regained control of the Louisiana Territory, it began implementing new laws and regulations in its largest cities, specifically New Orleans. New Orleans was one of the largest ports in the gulf, and it served as a major hub for importing and exporting goods.

The fledgling American nation relied heavily on New Orleans to both receive new goods as well as to sell its own goods to Europe. Jefferson feared that over time France would impose harsh taxes and other restrictions on American use of the port, but instead of declaring war with France to seize the land, he opted to purchase it instead. France ultimately agreed and altered the deal to include significantly more land.

"With the Louisiana Purchase in 1803, the United States purchased approximately 828,000,000 square miles of territory from France, thereby doubling the size of the young republic. What was known as Louisiana Territory stretched from the Mississippi River in the east to the Rocky Mountains in the west and from the Gulf of Mexico in the south to the Canadian border in the north. Part or all of 15 states were eventually created from the land deal, which is considered one of the most important achievements of Thomas Jefferson’s presidency."