Before any text information, a look at the territory:
When the French and Indian War ended in 1763, the French sway over Mississippi lands was over, the British took control, and turf battles with the Spanish continued for another 20 years, or so.
In 1783 the British (by treaty) gave their West Florida lands to Spain. Ironically, in 1783, the Treaty of Paris formally ended the American Revolutionary War, and in defeat, all British controlled lands (including most of Mississippi) were ceded to the U.S.
The Spanish kept their remaining lands for just a few short years as pressure from the fast-growing U.S. mounted, and by 1812, the United States controlled the entire Mississippi Territory, included all of Alabama, Mississippi and West Florida lands.
In 1817, the U.S. Congress divided this large territory into the State of Mississippi and the Alabama Territory. One year later Mississippi officially became the 20th U.S. State, and Alabama followed in 1819.