This dissertation examines how colonial border-making practices in British India changed pre-colonial conceptions of territory and shaped postcolonial borderlands in South Asia. It focuses on the disputed Indo-Tibetan borderland of Ladakh, now a fragmented part of Kashmir that long served as a gateway between the plains of India and Central Asia. The project begins with a survey of pre-colonial understandings of space in Ladakh. By examining an array of Ladakhi, Urdu, and English sources, the dissertation first reveals how local cosmologies, seasonal trade, and pastoralism shaped indigenous conceptions of territory. It then analyzes the strategies that the British colonizers deployed to transform the region into a frontier: boundary commissions, surveys, road building, trade regulation, and the production and restriction of “trans-frontier” information. Finally, it illustrates the problems produced by these processes, exposing the troubled inheritance of imperial frontiers for the modern nation-state. This dissertation makes four core interventions. It brings together macro-level historical studies on imperial frontiers and regional work on the northwestern Himalaya to examine the ways in which multiple modes of seeing space can cohabitate and conflict with each other, producing borderlands that simultaneously reflect the hegemony of the nation-state and the historical forces that undermine its limits. It also challenges political-theoretical and historical scholarship on territory that discounts the increasingly prominent role of applied geography in general, and border-making practices, specifically. Instead, this dissertation shows how geography played an intimate role in imperial state formation and, when coupled with growing security concerns, gave birth to a new, geopolitical way of envisioning space. Thirdly, it introduces an alternative approach to borderlands studies, one focused on the production of the border itself rather than the socio-cultural aspects that produce a broader borderland region. And lastly, it offers a new approach to the global history of frontiers, one that reveals the colonial practices and ideas that helped to shape postcolonial borders. By approaching the history of borders and frontiers as a complex of practices and ideas one can better understand the active legacies of empires in today’s postcolonial nation-states.