I exploit the expansion of the railroad network in 19th century Argentina to study the relationship between migration costs, migrations and economic mobility. I first study the responsiveness of migration decisions to migration costs. That is, did internal migrants respond to the availability of railroads? If so, how large was their response? Railroad construction might have affected not only the size but also the composition of the immigrant flow. The second part of my analysis then studies the influence of railroad construction on the selection of internal migrants. In particular, one plausible hypothesis is that lower migration costs might have increased migration rates among the poor, who were more likely to be credit-constrained. Finally, I look at the effect of railroad construction on economic mobility. Because place of residence influences economic outcomes, barriers to geographic mobility are also likely to hurt economic mobility. I test this hypothesis by looking at how the decrease in these barriers brought by railroad construction affected the association between the economic status of parents and their children.