The Priory Saint-Ouen was founded around 1066 by Hugues de Chaumont, who gave the priory to the monastery Marmoutier. Over time, the Franciscans (ordo fratrum minorum recollectorum), the Trinitarian Order and the Ursulines had branches in Gisors. [
Around 1095, the Duke of Normandy and King of England William II (Guillaume II le Roux) built an octagonal donjon to defend the borders. The castle Gisors was one of the numerous border patrols such as Dangu, Château -sur-Epte, Ecos, Baudemont and Gasny along the Norman Epte shore. On the French side lay the castles of Boury-en-Vexin, Saint-Clair-sur-Epte and La-Roche-Guyon. Gisors was the most important border fort in the north of the Norman Vexin. [6]
Due to its location, the town played several roles in the 12th Century in the signing of peace treaties between the King of France and the King of England, who was also the Duke of Normandy.
Peace of Gisors 1113
Peace of Gisors 1180
Peace of Gisors 1188
Castle ruin Gisors
In a field between Gisors and Courcelles on September 28, 1198 a battle between the English king Richard the Lionheart and the French king Philip II took place. Philip II (1165-1223) did not use the old, octagonal donjon, but had a new, circular donjon built, called the Tour du prisonnier ("prisoner's tower"), because a prisoner was there at the time of the Huguenot wars (1562- 1598) has carved numerous reliefs in the walls of his cell.
Gisors was converted several times into a Comté or a Duché. At the beginning of the 14th century was the heyday of Gisors. Tanneries and weaving mills of the city led to economic growth. Gisors was the seat of one of the seven major Bailliages of Normandy and seat of a Vicomté.