This article explores the 'unsettling' qualities of American writer Denis Johnson's 2011 novella, Train Dreams. It explores the book's engagement with environmental crises and indigenous cosmologies to show how the metaphysical insecurities, common to much of Johnson's fiction, come in this context to challenge the very concept of American nationhood itself-or as the novella's title parodies, the 'American Dream'. Train Dreams unsettles what I call the narrative infrastructures undergirding the story of the American frontier-becoming-nation-state: the transcontinental railroads, and the colonial property regimes that those railroads both pursued and opened up. In three central sections, the article explores Johnson's unsettling of notions of property, then empire, and finally race. Through these readings, it shows how the novella finds its way to an indigenous critique of America as a settler colonial state. While previous critical discussions of the 'unsettling' qualities of Johnson's work have until now meant that word affectively, in this article my aim is therefore to emphasise its decolonizing momentum as well.