The Duchy of Holstein was established by a Scandinavian monarch under what union?
Duchy of Holstein The Duchy of Holstein (German: "Herzogtum Holstein" , Danish: "Hertugdømmet Holsten" ) was the northernmost state of the Holy Roman Empire, located in the present German state of Schleswig-Holstein. It was established when King Christian I of Denmark had his County of Holstein-Rendsburg elevated to a duchy by Emperor Frederick III in 1474. Holstein was ruled jointly with the Duchy of Schleswig by members of the Danish House of Oldenburg for its entire existence.
Magnus, Duke of Saxony Magnus (  1045 – 23 August 1106) was the duke of Saxony from 1072 to 1106. Eldest son and successor of Ordulf and Wulfhild of Norway, he was the last member of the House of Billung.