Telling the story of a great Alpine valley in the Middle Ages is a perilous exercise that had never been attempted: A territory is a geographical unit but not a political one. Torn between the history of the different municipalities and that of Dauphiné, the medieval past of the Grésivaudan valley brings together very dissimilar situations: the communities of Haut Grésivaudan suffered for two hundred years from their border situation, while at the same time, already prosperous villages like Montbonnot or Montfleury know the banal existence of people without history. As for the villages of the balcony of Belledonne, they are part of the county of Geneva for a large part of the period studied! The author has chosen to tell an event story to better follow the course of the vicissitudes which have forged the destiny of this valley.