The project will study the poorly documented relationship between geographic and social mobility and their consequences on spatial inequalities. In particular, it will analyze the sources of spatial sorting as well as the role of transportation infrastructure on geographic and social mobility, for two countries with different spatial and political organizations, France and the United States, and for two contrasting periods, the 19th century and the second half of the 20th century. The research team will adopt a multidisciplinary approach and will rely on rich, localized and original historical data, such as information on the evolution of travel speeds. In particular, the project will focus on the role of transportation infrastructure development on local economic and demographic growth, the relocation of individuals and families across space, and access to opportunities (education and work).