Adams–Onís Treaty

What it is

Signed February 22, 1819, by Secretary of State John Quincy Adams and Spanish ambassador Luis de Onís, this treaty transferred Florida to the United States and fixed the first transcontinental boundary between the U.S. and Spanish territory. It took full effect in 1821.

Why it matters

The treaty was negotiated under President James Monroe, following the United States' occupation of Florida during conflict with the Seminole. It ended years of border disputes stemming from Pinckney's Treaty and the Louisiana Purchase, and extended U.S. claims to the Pacific while Spain gave up claims to the Oregon Country. The agreement reflects Adams's broader goal of removing European rivals from North America, a goal closely tied to the Monroe Doctrine issued a few years later.

Look closer

• Why might Spain have been willing to give up Florida at this particular moment?
• What does the map's depiction of the new boundary tell you about competing claims in North America?
• Whose presence on this land before the treaty is left out of the map?