 The creation of the Val-d'Oise department led to the establishment of the diocese of Pontoise on 9 October 1966 and the consequent elevation of the main church of the episcopal city to the rank of cathedral.Apart from the small group of cathedrals built as such in the territory of the present Île-de-France region, the church of Saint-Maclou can be considered as one of the area's most important buildings, both for its dimensions and for its architectural value, along with the Collegiate Church of Notre-Dame of Mantes-la-Jolie, the Collegiate Church of Notre-Dame-du-Fort of Étampes and the Collegiate Church of Saint-Martin of Étampes.The first study of it appeared in 1587, and it is one of the first five buildings on the territory of the present department of Val-d'Oise to be listed as a historical monument, in 1840.