Abstract: Christian Churches are among the longest lasting institutions inthe world. They had a strong impact on European history. One of the mostpowerful cultural transformations in modern history has been the dramaticexpansion of Christianity outside Europe. Recent, yet extensive, literatureuses Christian missions established during colonial times as a source ofexogenous variation to study the long-term effects of religion, human capitaland culture in Africa, the Americas and Asia. We argue that the endogeneity ofmissionary expansion may be underestimated, thus questioning the link betweenmissions and economic development. Using annual panel data on missions from1751 to 1932 in Ghana as well as cross-sectional data on missions for 43sub-Saharan African countries in 1900 and 1924, we show that: (i) locationaldecisions were driven by economic factors, as missionaries went to healthier,safer, and more accessible and developed areas, privileging the best locationsfirst; (ii) these factors may spuriously explain why locations with pastmissions are more developed today, especially as most studies rely onhistorical mission atlases that tend to only report the best mission locations.Our study identifies factors behind the spatial diffusion of religion. It alsohighlights the risks of omission and endogenous measurement error biases whenusing historical data and events for identification.