This chapter provides a geographical, ethnic, and economic overview of the coal mining frontier of Quảng Yên in northern Vietnam during the precolonial period, before large-scale coal mining began in the late nineteenth century. The first part of this chapter highlights the ethnic diversity, political volatility, rampant piracy, cross-border smuggling, and illicit trade that characterized this porous Sino-Vietnamese borderland, where state surveillance was often absent. The chapter also examines precolonial mining patterns, the Nguyễn dynasty’s mining policies, and the role of the Chinese in precolonial mining exploitation in Vietnam. Notably, the chapter attributes the decline of the precolonial mining economy in Vietnam to several environmental, political, and technological factors. The last part of this chapter documents the French struggle to stabilize and pacify this complex and volatile mining frontier in the late nineteenth century, paving the way for the region’s first large-scale coal mining enterprises and mining settlements.