Lotharii Regnum
The grandsons of Charlemagne split his Empire in the Treaty of Verdun of 843, which they prepared in the Basilica of St. Castor in Koblenz in 842. The left bank of the Rhine between Bacharach and Koblenz falls to Middle Francia. In 925, Middle Francia is finally becomes the Duchy of Lorraine within East Francia, the German Empire. The Rhine remains the heartland of the royal power, or as Otto of Freising called it, until in 1138 Conrad III is elected King of Germany in Koblenz, the first King of the House of Hohenstaufen.