From the site:
The year 2003 marks the bicentennial of the 1803 Treaty of France, by which the United States of America acquired the Louisiana Territory, an area of more than 828,000 square miles. Upon this acquisition, known as the Louisiana Purchase, the territory of the United States doubled. Historians consider the Louisiana Purchase to be a landmark event or turning point in American history. This Digest discusses (1) President Jefferson's decision to purchase the Louisiana Territory, (2) the significant consequences of this decision in American history, and (3) methods of teaching about the Louisiana Purchase.
THE DECISION TO PURCHASE LOUISIANA.
Jefferson had offered to buy for $2 million only the region around the mouth of the Mississippi River, which included the port and city of New Orleans. The President wanted to protect the interests of farmers in the Ohio River Valley, who depended on access to New Orleans. They sent their crops down the Mississippi River to New Orleans, from which ships took the products to cities along the Atlantic coast of the United States. Americans feared that the French might interfere with their trade by imposing high taxes on products and ships moving through New Orleans. Even worse, the French might close the port to Americans.