During the French Revolution, the Church’s properties were declared “national property”. The Benedictine monks were driven out and the Mont was rechristened the “Free Mont”. In 1811, the abbey became a house of detention with, mainly, common-law prisoners as well as some political prisoners. Closed in 1863, the prison had the effect of saving the building from destruction, although the monument was then in an advanced state of decay. In 1874, the abbey was classified as a 'Monument Historique' and a long restoration process began.