Why did colonial states set some border areas but not others? What explains the spatio-temporal dynamics of colonial expansion in Africa? While scholars have increasingly explored the long-term impacts of the colonization on contemporary economic development and conflict in recent years, the determinants of the territorial expansion and borders of colonial states remain relatively under-explored. Building upon the historical maps and GIS/remote-sensing techniques, this study develops an original georeferenced dataset of the expansion of colonial states in Africa and explores its drivers since the early 19th century. In particular, the initial empirical analysis focuses on the relative importance of socio-political factors (e.g., settlement patterns of ethnic groups) and structural factors (e.g., geographical conditions), with careful attention to the possible conditioning effect of the systemic uncertainty in the international system. This study makes two major contributions to the literature. First, it speaks to the emerging literature on the long-term impacts of artificial border design and ethnic partitioning in Africa on contemporary economic development and conflict. Although existing studies typically exploit colonial borders as sources of natural experiments, little provides systematic empirical evidence of the drivers of border design or the plausibility of the as-if random assumption. This study serves as a close empirical examination of the validity of the oft-employed research design. Second, our empirical analysis refines classic accounts of state building and colonial borders (e.g., Tilly 1990 and Herbst 2000). Drawing upon the methodological approach of historical GIS, this study presents novel empirical evaluation of theories of state building and expansion.
