Treaty of Lunéville
In the wake of the French Revolutionary Wars and the Treaty of Lunéville, the Holy Roman Empire underwent a process of substantial territorial reorganisation known as the German mediatization, under which Erfurt, since the 10th century a subject of the Electorate and Archbishopric of Mainz, was transferred to the Kingdom of Prussia, to compensate for territories Prussia lost to France on the Left Bank of the Rhine.