A historical region and former duchy of northern Germany and southern Denmark in southern Jutland. The duchy was created in 1115 and passed, along with the duchy of Holstein, to Christian I of Denmark in 1460. After subdivisions caused by complex hereditary holdings, the duchies were once more reunited under the Danish crown in 1773. Denmark, Prussia, and Austria contended for the region until 1866, when it was annexed by Prussia. In 1920 the northern part of Schleswig was returned to Denmark by plebiscite. The southern portion became (1946) part of the West German state of Schleswig-Holstein.