In the High Middle Ages, various powers attempted to rule over Heilbronn. The bishop of Würzburg in particular owned the church and possessed several rights. However, from 1225 onwards, King Henry (VII) and - at a later stage - King Rudolph succeeded in gaining control of the city. Over the course of the years it developed into an imperial city.
Thanks to its location on the banks of the Neckar River, Heilbronn became a regional trading centre. The expansion of the mills, the realignment of the Neckar River and the only bridge across the river for miles around all contributed to the wealth of the city.