The colonial making of African states’ geographies has limited their reach and caused currently low levels of development on the continent. However prominent this argument, no comprehensive data on local state reach and its evolution exists to date. This limits our understanding of the impact of changes in state reach on local development. I measure African states’ reach with travel times from cells on a continuous grid to their administrative capitals. Travel times are computed on the basis of a time-varying digital atlas of roads and national and regional governance units (1965–2015). With these data, I estimate the effect of changes in state reach on local education and infant mortality rates. Within the same location, both improve as travel times to its capitals, in particular the national capital, decrease. Coupled with simulations of counterfactual administrative geographies, the results show that the design of colonial borders and capitals curbed development, in particular in densely populated areas that are currently far away from their capitals.