Why are some communities able to come together to improve their collective lot while others are not? This book offers a novel answer to this question by looking at variation in local government performance in decentralized West Africa: local actors are better able to cooperate around basic service delivery when their formal jurisdictional boundaries overlap with informal social institutions, or norms of appropriate comportment in the public sphere demarcated by group boundaries. In this introductory chapter, I lay out the main contours of my theory as well as the implications that the argument holds for key debates in Comparative Politics, including the use of narratives as a lens into actors’ political strategies, the social identities we prioritize in our research, prospects for state-building in sub-Saharan Africa, and our understanding of how historical legacies shape contemporary development outcomes.