This study concerns the Benedictine monastery of Sant' Ambrogio in Milan, a unique and important institution because it was the first monastery in Italy to be founded under the aegis of the Carolingian family (c. 879). It is the first book-length study in English of one of the most important groups of early Italian charters, a type of document now widely acknowledged to be full of information about the social history of what were once imagined to be the Dark Ages. Using detailed evidence of some 300 charters, the book develops the thesis that Sant' Ambrogio played an essential part in the development and expansion of a complex urban society at Milan in the Carolingian period because the monks touched the lives of both "great men" and the "new society" of notaries, merchants, judges and moneyers. This book challenges the widely-held view that urban monasteries were less important in ninth-century political history than the great rural houses such as Fulda, St Gallen, Bobbio and San Vicenzo al Volturno.