The Duchy of Holstein was established by a Scandinavian monarch under what union?
Christian I of Denmark Christian I (February 1426 – 21 May 1481) was a Scandinavian monarch under the Kalmar Union. He was King of Denmark (1448–1481), Norway (1450–1481) and Sweden (1457–1464). From 1460 to 1481, he was also Duke of Schleswig (within Denmark) and Count (after 1474, Duke) of Holstein (within the Holy Roman Empire). He was the first Danish monarch of the House of Oldenburg.
Counts of Stade The Counts of Stade were members of the Saxony nobility beginning in the 10th century. Stade had developed since the 8th century as a principal center of trade and communications. The Counts of Stade created their domain between the lower Elbe and Weser rivers. They extended their power northwards with the acquisition of Dithmarschen in the 11th century. They became the Margraves of the Nordmark (Northern March) in 1056. There is also a close political and familial relationship between the Counts of Stade and the Counts of Walbeck. The county of Stade and Northern March were replaced by the March of Brandenburg by Henry the Lion, Duke of Saxony, in the 12th century. The family of Counts of Stade is referred to as the House of Udonids.