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 Alabama
More than a decade later, during the American Revolutionary War, the British informally ceded this West Florida region to Spain. By the Treaty of Versailles, September 3, 1783, Great Britain formally ceded West Florida to Spain. By the Treaty of Paris (1783), signed the same day, Britain ceded to the newly established United States all of this province north of 31°N, thus laying the foundation for a long controversy.
By the Treaty of Madrid in 1795, Spain ceded to the United States the lands east of the Mississippi between 31°N and 32°28'N. Three years later, in 1798, Congress organized this district as the Mississippi Territory. A strip of land 12 or 14 miles wide near the present northern boundary of Alabama and Mississippi was claimed by South Carolina, as part of the eastern colonies' previous hopeful extensions to the west. In 1787, during constitutional negotiations, South Carolina ceded this claim to the federal government. Georgia likewise claimed all the lands between the 31st and 35th parallels from its present western boundary to the Mississippi River, and did not surrender its claim until 1802. Two years later, the boundaries of Mississippi Territory were extended so as to include all of the Georgia cession.