Which president signed the Louisiana Purchase treaty for the United States in 1803?

Thomas Jefferson signed the Louisiana Purchase treaty for the United States in 1803.

Jefferson was president when American diplomats Robert Livingston and James Monroe negotiated with France. The administration initially hoped to secure New Orleans and nearby territory, but France offered the much larger Louisiana Territory. Jefferson approved the agreement even though the Constitution did not explicitly describe a procedure for acquiring foreign territory.

The treaty was signed in Paris on April 30, 1803, and the Senate ratified it later that year. The transfer formally took place in December 1803. Jefferson then supported exploration, including the Lewis and Clark Expedition, to investigate the new lands and routes to the Pacific.

The purchase is associated with territorial expansion, but the area was already home to many Indigenous nations and included communities with French, Spanish, African, and Native cultural roots. Its long-term consequences therefore involved diplomacy, migration, slavery, and conflict as well as national growth.