West Florida controversy

The West Florida Controversy refers to two border disputes that involved Spain and the United States in relation to the region known as West Florida. The first dispute commenced immediately after Spain received the colonies of West and East Florida from the Kingdom of Great Britain following the American Revolutionary War, and continued for nearly four decades. Initial disagreements were settled with Pinckney's Treaty of 1795.

The second dispute arose following the Louisiana Purchase in 1803. The controversy led to the secession of part of West Florida, known as the "Republic of West Florida," from Spanish control in 1810, and its subsequent annexation by the United States. In 1819 the United States and Spain negotiated the Adams–Onís Treaty, in which the United States purchased the remainder of Florida from Spain.

Britain formed the territory of West Florida out of territory it received from Spain and France in the 1763 Treaty of Paris, which ended the French and Indian War (the Seven Years' War). In this treaty it received all of Spanish Florida from Spain, and nearly all of French Louisiana east of the Mississippi River from France. Finding the new territory too big to govern from one capital, the British divided it into two new colonies: West Florida, with its capital at Pensacola, and East Florida, with its capital at St. Augustine.

...
Wikipedia