Sparsely populated British Florida had stayed loyal to Crown during the American Revolutionary War, and by the terms of the Treaty of Paris that ended the war, the territory is returned to Spain in 1783.

After a brief diplomatic border dispute with the fledgling United States, the countries set a territorial border and allow Americans free navigation of the Mississippi River by the terms of Pinckney's Treaty in 1795.

France sells Louisiana to the United States in 1803.

The U.S. claims that the transaction includes West Florida, while Spain insists that the area is not part of Louisiana and is still Spanish territory.

In 1810, the United States intervenes in a local uprising in West Florida, and by 1812, the Mobile District is absorbed into the U.S. territory of Mississippi, reducing the borders of Spanish Florida to that of modern Florida.

In the early 1800s, tensions rise along the unguarded border between Spanish Florida and the state of Georgia as settlers skirmish with Seminoles over land and American slave-hunters raid Black Seminole villages in Florida.

These tensions are exacerbated when the Seminoles aid Great Britain against the United States during the War of 1812 and lead to American military incursions into northern Florida beginning in late 1814 during what becomse known as the First Seminole War.

As with earlier American incursions into Florida, Spain protests this invasion but cannot defend its territory, and instead opens diplomatic negotiations seeking a peaceful transfer of land.

By the terms of the Adams-Onis Treaty of 1819, Spanish Florida ceases to exist in 1821, when control of the territory is officially transferred to the United States.