An unexplored dataset has been utilized to analyse the colonists who settled in southern Lazio during the Integral Land Reclamation carried out by the fascist regime in the 1930s. The farm records, known as Schede Poderali, encompass the contracts through which selected families were allocated portions of land reclaimed from the marshes. The documents enabled us to delineate the population trends in the decades following marsh reclamation and immigration from other Italian regions. This new piece of information enriches scientific research on the area providing an empirical validation of the interplay between population dynamics and political action.