We study the impact of transportation infrastructure on agriculture and development in colonial Ghana. Two railway lines were built between 1901 and 1923 to connect the coast to mining areas and the large hinterland city of Kumasi. This unintendedly opened vast expanses of tropical forest to cocoa cultivation, allowing Ghana to become the world's largest producer. This attracted migrants to producing areas and the economic surplus drove urbanization. Using data at a very fine spatial level, we find a strong effect of railroad connectivity on cocoa production due to reduced transportation costs. We then show that the economic boom in cocoa-producing areas was associated with demographic growth and urbanization. We _nd no spurious effect from lines that were not built yet, and lines that were planned but never built. We show that our results are robust to considering nearest neighbor estimators. Lastly, railway construction has durably transformed the economic geography of Ghana, as railway districts are more developed today, despite thirty years of marked decline in rail transportation.