The Spanish Cession: How Many Square Miles Did Florida Add to the U.S.?

The Spanish Cession (Adams–Onís Treaty, 1819) transferred Florida from Spain to the United States. The territory ceded encompassed approximately 76,000 square miles (196,800 km²).

What Was Included

• East Florida (capital St. Augustine) — roughly the peninsula east of the Suwannee River.
• West Florida (capital Pensacola) — the panhandle west to the Perdido River.
• Spain also relinquished claims to the Oregon Country (north of 42° N), though this was not part of the Florida land area.

U.S. Concessions

• Assumed $5 million in U.S. citizen claims against Spain.
• Renounced claims to Texas (west of Sabine River) — later a flashpoint.

Significance

Completed U.S. control of the Gulf Coast east of the Mississippi, secured Spanish recognition of U.S. Louisiana Purchase boundaries, and set the stage for Florida's territorial period (1821) and statehood (1845).