Le Vexin

Historic region of northwest France on the right bank of the Seine, now in the départements of Val-d'Oise, Oise, and Eure. Traditionally an agricultural plain, the area has experienced urban development in the late 20th century.

History By the Treaty of St-Clair-sur-Epte in 911 it was divided into Le Vexin Normand, the capital of which was Gisors; and Le Vexin Français, the capital of which was Pontoise. In the 12th-century struggles between the houses of Blois and Anjou, in which Henry II of England was involved, Le Vexin Normand was the strategic key to Rouen. Geoffrey of Anjou (father of Henry II of England), under whom Anjou and Normandy were united, had ceded it to the king of France, but Henry regained it though a treaty with Louis VII.

John (later king of England) transferred Le Vexin again in 1195 to Philip II of France; and Richard I had to build the great fortress at Les Andelys to replace the lost fortress and natural defences of Le Vexin.