Prince-Archbishop Adalbert of Hamburg-Bremen. The Imperial Abbey held the rank of principality, and Heppenheim developed over time into the territory's administrative and economic hub, although it lost its importance with the Abbey's downfall in the 11th and 12th centuries. In 1229, Emperor Friedrich II put the Starkenburg under the administration of the Archbishops of Electoral Mainz, doing likewise with the Lorsch Abbey along with Heppenheim in 1232. But for an interruption from 1461 to 1623 when the fief was pledged to the Electorate of the Palatinate, Heppenheim remained an Electoral Mainz holding right up until the Reichsdeputationshauptschluss in 1803. Then it became Hessian, first part of the Landgraviate of Hesse-Darmstadt, and since 1948 it has been part of the Bundesland of Hesse. Heppenheim has had town rights since at least 1318, and market rights, it is believed, already by the early 9th century. From 1265 (possibly earlier) until 1803, Heppenheim was the seat of the Electoral Mainz Amt (Oberamt) of Starkenburg. Once it passed to Hesse-Darmstadt, the Amt was abolished. Heppenheim was thereafter first the seat of a (much smaller) Amt, and then, as of 1821 the seat of the Heppenheim Administrative Region (Landratsbezirk). As of 1832 it was the seat of the Heppenheim district. Since then, it was between 1848 and 1852 the seat of the Regierungsbezirk of Heppenheim, and has been since 1938 the seat of the Bergstraße district, to which were assigned not only the old Heppenheim district, but also great parts of the likewise abolished Bensheim district, with the parts of the Worms district on the Rhine’s right bank being added after the Second World War. In both 1369 and 1693 (in the latter case owing to the devastation wrought by the French in the Nine Years' War), Heppenheim was almost utterly destroyed in town fires. The town came through both world wars unscathed, aside from slight damage when the Americans marched in March 1945. Heppenheim suffered severely in the Thirty Years' War (1618–48); the Starkenburg was overwhelmed by Spanish troops in 1621, and by the Swedes in 1630. The Plague killed about 80% of the population in 1635 (almost 100% in the outlying countryside), and the town was sacked by the Poles in 1636 and again in 1645 by the French. The Heppenheim Conference (Heppenheimer Tagung), a meeting of leading liberals on 10 October 1847 in the Halber Mond (“Half Moon”) Hotel, was a prelude