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.
Schleswig-Holstein-Sonderburg-Beck Schleswig-Holstein-Sonderburg-Beck (Schleswig-Holstein-Beck for short) was a line of the Schleswig-Holstein-Sonderburg branch of the House of Oldenburg. It consisted of August Philipp, Duke of Schleswig-Holstein-Sonderburg-Beck (1612-1675) and his male-line descendants. Schleswig-Holstein-Glücksburg, to which several present-day royal houses belong, is a branch of Schleswig-Holstein-Beck.