Seligenstadt had its first documentary mention on 11 January 815 in a donation document, under its then current name of "Obermühlheim". The town was founded by Charlemagne’s biographer Einhard. After he had acquired the Frankish settlement of "Obermulinheim" from Louis the Pious in 815 as a donation, he founded a Benedictine monastery here. Mentioned as an earlier owner is a Count Drogo. The bones of the martyrs Marcellinus and Peter, which had been stolen in Rome, were transferred from the basilica in Steinbach in the Odenwald to Obermühlheim, soon leading to a change in the community’s name from Obermühlheim to Seligenstadt ("town of the blessed ones" in German). About 830, building work began on the "Einhard-Basilika", the current version of which is now the landmark of Seligenstadt. Einhard died in 840 and he and his partner, Imma, are buried in a chapel in the northern transept of the church.