<p>Cross-border trade between India and Tibet historically connected the Himalayan borderlands through dense networks of exchange shaped by distinct ecological conditions, patterns of mobility, and customary social norms. Among the many commodities that circulated across these routes, salt from the Changthang plateau of Western Tibet and food grains from Kinnaur constituted a distinctive exchange system widely known as the salt–grain trade. Drawing on historical gazetteers, archival records, and spatial interpretation of trade routes, this paper examines how the ecological origins of these commodities generated a relationship of interdependence between pastoral communities in Western Tibet and the agro-pastoral society of Kinnaur. The study further argues that this exchange was not merely commercial but socially embedded, sustained through customary partnerships, seasonal trade fairs, and long-standing treaties. The repeated movement of salt and grain across high mountain passes produced a functional trans-Himalayan region that preceded, and in many ways contradicted, the boundaries later imposed by modern nation-states. Theoretically, the paper engages with symbolic geography to demonstrate how this borderland space was collectively perceived, imaginatively constructed, and reproduced through everyday practices of trade, mobility, and social exchange—offering an analytical corrective to state-centric approaches that have dominated border studies in high-altitude mountainous regions. By tracing the disruption of this system following the 1962 border closure and its limited revival after 1994, the paper shows how modern territorial boundaries transformed a historically porous frontier into a tightly regulated borderland, illuminating the broader reconfiguration of Himalayan cross-border relations in the modern era.</p>