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.
Tombigbee District
The British held West Florida until 1779–81, late in the American Revolutionary War, when it was captured by Spanish forces under the command of Bernardo de Gálvez. It formally became a Spanish possession with the 1783 Treaty of Paris, which also ended the American Revolution. This caused a boundary dispute between the United States (US) and Spain, with the U.S. claiming that the boundary between its territory and West Florida was at the 31st parallel north and Spain claiming it at 32 degrees 28 minutes of north latitude. Spain held the Tombigbee settlements until the Pinckney's Treaty in 1795, in which they agreed to the boundary at the 31st parallel north in return for other concessions by the US. It was ratified in the United States Senate on March 7, 1796 and by Spain on April 25, 1796, being proclaimed on August 3, 1796. The treaty stipulated that both countries would participate in a joint expedition to mark the agreed-upon boundary; President George Washington selected Andrew Ellicott as commissioner. The survey was completed in early 1800, although American settlers had already been pouring into the area since the proclamation of the treaty.