Duchy of Holstein

The Duchy of Holstein was the northernmost state of the Holy Roman Empire, located in the present German state of Schleswig-Holstein. It originated when King Christian I of Denmark had his County of Holstein-Rendsburg elevated to a duchy by Emperor Frederick III in 1474. Members of the Danish House of Oldenburg ruled Holstein – jointly with the Duchy of Schleswig – for its entire existence. From 1490 to 1523 and again from 1544 to 1773 the Duchy was partitioned between various Oldenburg branches, most notably the dukes of Holstein-Glückstadt (identical with the Kings of Denmark) and Holstein-Gottorp. The duchy ceased to exist when the Kingdom of Prussia annexed it in 1866 after the Austro-Prussian War. History The northern border of Holstein along the Eider River had already formed the northern border of the Carolingian Empire, after Emperor Charlemagne upon the Saxon Wars reached an agreement with King Hemming of Denmark in 811. The lands of Schleswig beyond the river remained a fief of the Danish Crown, while Holstein became an integral part of East Francia, the Kingdom of Germany and the Holy Roman Empire. Establishment