 The former diocese of Tortona was made part of the French department of Marengo.The three former cathedrals of the suppressed dioceses, including Tortona, were reduced to the status of Collegiate Churches and their Canons became members of Collegiate Chapters.On its re-establishment as a separate and independent diocese by the Bull "Beati Petri" (17 July 1817) of Pope Pius VII, the diocese was taken from the metropolitan see of Turin and made suffragan to Genoa.