This paper analyzes the influence of transportation infrastructure, and in particular of the Regional Express Rail (RER), on employment and population growth in the Paris metropolitan area between 1968 and 2010. In order to make proper causal inference, we rely on historical instruments and control for all other transportation modes that could be complement or substitute to the RER. A dynamic analysis accounting for spatial heterogeneity reveals that for municipalities located less than 13 kilometers from an RER station, each kilometer closer to the station increases employment and population growth by 12% and 8% respectively. Regarding the time pattern of these effects, we find no impact of the RER expansion on employment growth during the first part of the period, while the effect on population growth appears earlier but declines over time.