In colonial Southeast Asia, the process of enclosure aimed to integrate communities living in the borderlands, along with their lands and resources, into the state project. In 1891, the newly established French colonial administration in Tonkin (northern Vietnam) decided the upland region bordering China should be physically and administratively enclosed to achieve these aims. The governor general ordered the French military to administer these borderlands and to complete two surveys of local ‘tribes’ in 1897–1898 and 1903–1904 to make upland populations and their livelihoods more legible and, the administration hoped, more controllable. By examining details of these surveys, we not only obtain proof of this enclosure project but we also gain rare insight into and a snapshot of upland border livelihoods at the turn of the 20th century. The surveys reveal details regarding local cross‐border trade strategies, marketplace manoeuvres, the means by which the colonial government enforced a common currency and, despite such attempts, the enduring nature of barter. We probe how local populations reacted to the state's processes of legibility, and in particular, how upland residents adapted their trade livelihoods to the new realities of being included within the colonial state and, progressively, within the national economy.