Why do states grow stronger and more capable in some areas of their territory than in others? This dissertation examines the origins of domestic variation in state strength in Mexico and Colombia and shows that the geography of state power in each country reflects historical lines of political antagonism. Challenging prevailing geographic and economic explanations of the reach of the state, it traces the uneven development of state capacity across territory and functions to sharp domestic cleavages that organize state-building efforts and societal reactions to the state during formative historical periods. The dissertation argues that partisanship is a pervasive force in the state’s penetration of territory and society, but partisanship spawns different territorial patterns of state capacity across constituent dimensions of the concept. The result is that, unlike conventionally assumed, not all types of state capacity hang together at the sub-national level. The study pursues this argument empirically relying on new, geo-referenced, and highly disaggregated historical datasets for both Mexico and Colombia, collected through intensive archival research and spanning various domains of state activity. Using historical analysis and statistical methods, I demonstrate the connections between the religious cleavage that split Mexican society in the aftermath of the Revolution and the state’s subsequent ability to extract fiscal revenue, monopolize the means of violence at the local level, provide law and order, allocate land, and educate its citizens across territory. Similarly, I show that the historical hegemonic struggle between the Liberal and Conservative Parties in Colombia impressed a squarely partisan logic into state development in key domains like taxation and education. In both cases, the study documents that intense political struggles during state formation made states develop unevenly across geography and institutional arenas simultaneously, with legacies that extend to this day. The dissertation’s findings are significant for our understanding of state-building, the varying ability of states to enhance citizens’ welfare, and the origins of institutional weakness.