The first written source describing the site under the name dates back to the 6th century. It was transformed into a fortified castle by Eudes the First count of Blois in 990. In 1001, it was taken by the Anjou realm, and Foulques Nerra gave it to Gautier I of Montsoreau. Gautier I belonged to one of the most pre-eminent families of Anjou. Thus, the "Castrum Monsorelli" became one of the forty fortified castles in Anjou and one of the few to be given the title of lordship at the turn of year 1000. A town developed quickly near the castle and in the "narratio de commendatione Turonice provincie", edited by Salmon in 1854, the site was mentioned as one of "oppidis munitissimi et populosis" by the second half of 11th century. A right to raise tax was attested in written sources from the 12th century.