The town was built not far from the Gallo-Roman town of Alauna or Alaunia, from where the town derives its name. It was a fortified stronghold under the Norman dukes and French monarchs. Also here, William the Conqueror received the news that the barons of Cotentin and Bessin were conspiring to kill him, enabling him to escape to Falaise. Edward III of England took Valognes without resistance, spent one night there and then pillaged and burnt the city. Henry III of England possessed the town, which remained under English rule for thirty years. It would be a kind of resort for English aristocratic visitors until the 1920s. During the French Wars of Religion, (1588) Valognes sided with the Catholic League. The castle, like that of Cherbourg, was completely destroyed under Louis XIV. Of the convent of the Capuchins and Cordeliers and the abbey of Benedictine nuns, which existed in Valognes prior to 1792, only the latter remains, transformed into the hospice of the Rue des Religieuses.
Before the French Revolution, Valognes was the residence of more than a hundred families of distinguished birth and fortune, and was for a long time afterwards the home, en villégiature, of many of the old noblesse. Thus the town was known as the Versailles of Normandy for its aristocratic mansions and palaces, as well as the quiet, mysterious ambience and exclusivity its streets. This was the Valognes of Barbey d'Aurevilly.
The 1928 Methuen guide book to Normandy by Cyril Scudamore rather more prosaically describes Valognes as "a clean and well-built town, whose fine old houses bear witness to its former prosperity".
Little remains of Valognes' famous architectural heritage as many of the aristocratic mansions were reduced to rubble during the battle of Normandy. The lovely hôtel de Beaumont, however, still stands.