Adams-Onís Treaty

American copy of the 1819 treaty establishing the border between the United States and New Spain

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Signed in 1819 by John Quincy Adams and Luis de Onís, the Adams-Onís Treaty between the United States and Spain gave Florida to the U.S. and established the Sabine River as the border between the U.S. and New Spain. 

The formation of Texas was part of a global story. The boundaries of European land claims changed as a result of wars in Europe, revolutions in the colonies, and the birth of the United States. When the French sold Louisiana to America with the Louisiana Purchase in 1803, many Americans believed the sale included Texas. These claims were based on La Salle's failed attempt to colonize Texas in the 1680s. The Adams-Onís Treaty put those claims to rest, ceding Texas to Spain. However, many Americans did not agree with the treaty. Some U.S. citizens argued the border should be at the Rio Grande. Many individuals and families from the east settled in Texas illegally, which was still part of Spanish-controlled Mexico. 

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Adams-Onís Treaty Artifact from Washington, DC
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