This chapter identifies the colonial origins of the institutional structures and patterns of uneven economic development that create the template for political regionalism in African countries. Functional economic regions and administrative regions tended to align in African colonies, defining patterns of regional difference and inequality that are often strongly visible today. This process established frameworks within which politically salient ethnic identities developed, and defined political constituencies in territorial terms. With the 1940s emergence of colony-wide politics, existing administrative and political structures channeled regional interests and ideologies of regional consciousness into the national arena. A boundary persistence analysis underscores the large extent to which colonial territorial grids have been reproduced over time. I explain this persistence in terms of how African political leaders, social elites, farmers, and members of rural communities found advantage in territorial institutions forged under colonialism. These regional cleavages and the territorial institutions that help to reproduce them have structured patterns of national-level political competition in many African countries for many decades.