The Territory of Mississippi was an organized incorporated territory of the United States that existed from April 7, 1798, until December 10, 1817, when the western half of the territory was admitted to the Union as the State of Mississippi. The eastern half was redesignated as the Alabama Territory until it was admitted to the Union as the State of Alabama on December 14, 1819. The Chattahoochee River played a significant role in the definition of the territory's borders. The population rose in the early 1800s from settlement, with cotton being an important cash crop.