Frederick I, Holy Roman Emperor
In 1184 Frederick I, Holy Roman Emperor held one of the biggest diets of the Middle Ages at the Maaraue in Kostheim, the Diet of Pentecost. Occasion had been the promotion to Knighthood of is both sons Henry hand Frederic, Duke of Swabia. During the Siege of Mainz by Prussian and Austrian troops in the Napoleonic Wars Kostheim had been severely damaged several times. In the cause of the bombing of Mainz in World War II Mainz-Kostheim was subject to air raids.