The viscounts were entrusted with the government of the county of Châteaudun, records of whom are continuous from the mid-10th century.
The actual rule of Châteaudun between the late 9th and the mid-10th centuries, and the relationships between the count and viscounts, is uncertain.
The county was revived in 1439 when the region was recreated as the County of Dunois and granted to Jean Levieux Valois des Orléans (Jean de Dunois), the illegitimate son of Louis I, Duke of Orléans, son of Charles V of France.
The family tree of the House of Châteaudun is most illustrative of these relationships.
The lineage of the counts of Anjou, who acquired the land by the marriage of a grandson of Fulcois, Geoffrey II of Gâtinais, with Ermengarde of Anjou, heiress of the House of Ingelger, continued on to modern times.