Capital's commodity frontiers strategy has at once woven together regional differences within an expanding world‐system and remade the productive and reproductive activities of humans and the rest of nature. The development of successive commodity frontiers gave way to long waves of economic expansion that have been pivotal to accelerating accumulation and transcending capital's recurrent crises. In short, commodity frontiers are constitutive of world‐ecological moments premised on booms and crises of accumulation. In this paper, I examine the coal commodity frontier in Appalachia, to illustrate the region's history as one of succeeding frontiers in and out of the region over the long twentieth century of American capitalism. I argue that the origin of Appalachia's coal frontier was decisively made through the nineteenth‐century agricultural revolution expressed outside of the region. Appalachia's full‐fledged development was an outcome of capital's under‐reproduction strategies. The crisis of the region's frontier turned on a lack of surplus from under‐reproduction strategies, competing coal basins, economic diversification and competing energy sources. I find that the commodity frontier concept not only illuminates regional political economies and ecologies of difference, but also explains the production of nature of historical capitalism.