US National Archives
Our Documents: The Louisiana Purchase Treaty (1803)
A fantastic site from the Our Documents group that allows visitors to see an original copy of the Louisiana Purchase Treaty of 1803. This treaty allowed the United States to purchase a tract of land west of the Mississippi River that was...
Other
Gateway New Orleans: Louisiana Purchase
Read a description of the terms of the Louisiana Purchase. There is a map to show the land that was included in this deal.
Library of Congress
Loc: America's Story: Louisiana Purchase
This Library of Congress timeline series discusses the Louisiana Purchase.