The paper provides evidence of the causal effect of infrastructure on trade costs, for the 107 Italian provinces (NUTS3), testing whether current differences in trade costs among provinces can be traced back to the structure of the historical Roman road network. By constructing a specific measure of the extent of the Roman road network for each Italian province and relying on an instrumental variables approach, the empirical analysis shows that having an integrated road system, as the one built during the Roman Empire, plays an important role in current international trade. The study confirms not only the importance of history for contemporary economic development, but also the significant role played by the historical infrastructure in shaping geography and in determining current trade patterns via the influence on today’s infrastructure.