All of the area of Mississippi except the part south of the 31st parallel was included in the original territory of the United States. The United States claimed the territory south of the 31st parallel as part of the Louisiana Purchase in 1803. Mississippi Territory was organized on April 7, 1798, from unorganized area; it included area west of Georgia to the Mississippi River, comprising the southern third of the present-day states of Alabama and Mississippi. The territory annexed the northern part of the same two future states when Georgia ceded its western claims in 1802 and the lands south of the 31st parallel in 1812. Mississippi Territory was reduced by the organization of Alabama Territory in 1817. Mississippi was admitted to the Union on December 10, 1817, as the 20th state, with generally the same boundary as the present state, although jurisdiction over the entire area was not formally accomplished until Spain relinquished its claims to the southern portion of the state in 1819.