Florida
Florida had become a burden to Spain, which could not afford to send settlers or garrisons. Madrid therefore decided to cede the territory to the United States through the Adams–Onís Treaty, which took effect in 1821. President James Monroe was authorized on March 3, 1821 to take possession of East Florida and West Florida for the United States and provide for initial governance. Andrew Jackson, on behalf of the U.S. federal government, served as a military commissioner with the powers of governor of the newly acquired territory for a brief period. On March 30, 1822, the U.S. Congress merged East Florida and part of West Florida into the Florida Territory.
By the early 1800s, Indian removal was a significant issue throughout the southeastern U.S. and also in Florida. In 1830, the U.S. Congress passed the Indian Removal Act and as settlement increased, pressure grew on the U.S. government to remove the Indians from Florida. Seminoles offered sanctuary to blacks, and these became known as the Black Seminoles, and clashes between whites and Indians grew with the influx of new settlers. In 1832, the Treaty of Payne's Landing promised to the Seminoles lands west of the Mississippi River if they agreed to leave Florida. Many Seminole left at this time.
History of Pensacola, Florida
After the transfer of the vast Louisiana Territory from Spain to France at the end of the 18th century, and the subsequent purchase of the region by the United States in 1803, Spanish East and West Florida were surrounded by American Southern states and territories. Anglo-American settlement of West Florida increased and the Spanish, busy with growing rebellions throughout Mexico and South America, were not able to focus on fortifying the region. In 1810, American settlers in the part of Florida west of the Pearl River (today the boundary between Louisiana and Mississippi) declared the West Florida Republic a state independent from Spain. The region was annexed into the new state of Louisiana in 1812.