Spain Ceded Florida to the U.S. via the Adams-Onís Treaty (1819)

Spain did not "sell" Florida in a simple transaction. The transfer was formalized by the Adams-Onís Treaty of 1819 (ratified 1821), also known as the Transcontinental Treaty.

Key terms:

• Spain ceded East and West Florida to the United States.
• The U.S. assumed $5 million in claims by American citizens against Spain.
• The U.S. renounced claims to Texas (setting the Sabine River boundary).
• Spain received no direct cash payment; the $5 million was debt forgiveness.

Motivations: Spain, weakened by the Peninsular War and Latin American revolts, could not defend Florida against American expansion and Seminole raids. The U.S. sought to eliminate a haven for runaway slaves and hostile tribes and to secure its southern border.