In 1812, Congress added the Mobile District of West Florida to the Mississippi Territory, claiming that it was included in the Louisiana Purchase. The following year, General James Wilkinson occupied the Mobile District with a military force. The Spanish did not resist. Thus the whole area of the present state of Alabama was taken under the jurisdiction of the United States. Several powerful Native American tribes still occupied most of the land, with some formal ownership recognized by treaty with the United States. Five of the major tribes became known as the Five Civilized Tribes, as they had highly complex cultures and adopted some elements of European-American culture.