Perched on a limestone spur, protected to the north, west and south by marshes, from the Middle Ages it was one of the most important fortresses in Normandy.
Argentan was built by Henry 1st of England, who was also Duke of Normandy, in the early 12th century.
From 1134 to 1618, the town was protected by two sets of battlements: the town battlements with their sixteen towers; and the castle battlements with four towers which enclosed the castle, the St Nicolas Chapel and the keep which are still in existence.
Within its ramparts, Argentan received famous people. Matilda, daughter of Henry 1st of England and married to Geoffrey Plantagenet, took refuge here in 1135. In 1172 Henry II of England, gathered all the counts and barons of the Duchy of Normandy to prepare the conquest of Ireland. In 1189, Eleanor of Aquitaine took up residence in the château of Argentan and received her two sons, Richard the Lion-heart and John Lackland.
A l'abri de ses remparts, Argentan a accueilli des personnages illustres. Mathilde, fille de Henri Ier, roi d'Angleterre et mariée à Geoffroy Plantagenêt, y trouve refuge en 1135. Henri II, roi d'Angleterre, réunit en 1172 tous les comtes et barons du duché de Normandie pour préparer la conquête de l'Irlande. En 1189, Aliénor d'Aquitaine fixe sa résidence au château d'Argentan et y reçoit ses deux fils, Richard Cœur de Lion et Jean sans Terre.