"This article places environmental history for the first time at the center of British India’s borderlands with a particular focus on the province of Sindh. Northern, or Upper, Sindh, defined by its proximity to mountainous tribal Balochistan, was an “external frontier,” whereas southeastern Sindh, located well within British India’s territorial boundaries, was an “internal frontier” where aridity and scarcity of population meant that there was little to support a strong state presence. Colonial policy on both frontiers used irrigation canals to effect environmental change and to establish stronger state control in areas where officials thought it insufficient. In southeastern Sindh, canal construction was a broader and deeper modernizing project than it was in the northern part of the province. These two contrasting frontier policies aimed to produce very different geographies of state space. A close investigation of canal policy written between 1850 and 1900 shows a clear aim to create a discursive and material distinction between Sindh as the interior of the empire and Balochistan as exterior. Analyzing a frontier’s inward or outward orientation helps us understand how frontier policy is developed and executed."