The Louisiana Purchase nearly doubled U.S. territory in 1803, expanding the national story toward America250.
The United States agreed to acquire the Louisiana Territory from France in 1803. President Thomas Jefferson had initially sought New Orleans and access to the Mississippi River, but French negotiators offered the much larger territory. The purchase was formally completed through treaties signed in April and May 1803.
The acquisition covered about 827,000 square miles, extending U.S. claims west of the Mississippi River to the Rocky Mountains and north toward present-day Canada. It included all or parts of fifteen present-day U.S. states and two Canadian provinces.
The purchase raised constitutional and political questions for Jefferson’s administration, and its boundaries were initially uncertain. It also created new conflicts over Indigenous sovereignty, slavery, settlement, and the future balance between regions—issues that continued shaping the United States long after the founding generation.