カノッサの屈辱
In 765, the first documented mention of the Frankish village was recorded in the Lorsch Codex, in connection with an endowment by Charlemagne to the Lorsch Abbey. Further portions of Oppenheim were added to the endowment in 774. In 1008, Oppenheim was granted market rights. In October 1076 Oppenheim gained special importance in the Investiture Controversy. At the princely session of Trebur and Oppenheim, the princes called on King Henry IV to undertake the "Walk to Canossa". After Oppenheim was returned to the Empire in 1147, it became a Free Imperial City in 1225, during the Staufer Emperor Frederick II's. At this time, the town was important for its imperial castle and the Burgmannen who lived there.