The Elector of Mainz was one of the seven Prince-electors of the Holy Roman Empire. As both the Archbishop of Mainz and the ruling prince of the Electorate of Mainz, the Elector of Mainz held a powerful position during the Middle Ages. The Archbishop-Elector was president of the electoral college, archchancellor of the empire, and the Primate of Germany as the papal legate north of the Alps, until the dissolution of the empire in 1806. The origin of the title dates back to 747, when the city of Mainz was made the seat of an archbishop, and a succession of able and ambitious prelates made the district under their rule a strong and vigorous state. Among these men were important figures in the history of Germany such as Hatto I, Adalbert of Mainz, Siegfried III, Peter of Aspelt and Albert of Brandenburg. There were several violent contests between rivals for the archbishopric, and their power struggles occasionally moved the citizens of Mainz to revolt. The lands of the elector lay around the city of Mainz on both banks of the Rhine; their area reached 3200 sq. miles by the end of the Empire. The last elector was Karl Theodor von Dalberg, who lost his temporal power when the archbishopric was secularized in 1803. Elector of Mainz (1356–1803) The Archbishop of Mainz was an influential ecclesiastic and secular prince in the Holy Roman Empire between 780–782 and 1802. In Church hierarchy, the Archbishop of Mainz was the primas Germaniae, the substitute for the Pope north of the Alps. Aside from Rome, the See of Mainz is the only other see referred to as a "Holy See", although this usage became rather less common. This archbishopric was a substantial ecclesiastical principality of the Holy Roman Empire. The ecclesiastical principality included lands near Mainz on both the left and right banks of the Rhine, as well as territory along the Main above Frankfurt (including the district of Aschaffenburg), the Eichsfeld region in Lower Saxony and Thuringia, and the territory around Erfurt in Thuringia. The archbishop was also, traditionally, one of the Imperial Prince-Electors, the Arch-chancellor of Germany, and presiding officer of the electoral college technically from 1251 and permanently from 1263 until 1803. The see was established in ancient Roman times, in the city of Mainz, which had been a Roman provincial capital called Moguntiacum, but the office really came to prominence upon