Hersfeld was first mentioned as a market centre in 1142 and as a town in 1170. At this time also came the Hersfeld Abbey's greatest importance in Imperial politics. In the centuries that followed, the Abbey's might ebbed as after the Great Interregnum (1254–1273) it could no longer enjoy the Holy Roman Emperor’s support. Beginning in 1373, the Landgraviate of Hesse acquired influence over the town through defensive alliances. On "Vitalisnacht" (Saint Vitalis’s night, 27–28 April) 1378, the power struggle between the Abbey and the town reached its high point. Because of the German Peasants' War in 1525, great parts of the town and the Abbey passed to Hesse. In 1606, the last abbot died and in the Peace of Westphalia in 1648, the Imperial Abbey, raised to Electorate, was awarded to the Landgraviate of Hesse-Kassel. Hersfeld, now a worldly electorate, henceforth belonged to Hesse-Kassel.