The American frontier has long served as a safety valve, channeling domestic tensions outward into expansion, and historian Greg Grandin traces how the closing of that frontier has transformed national politics. From the Revolution through the conquest of the West, the removal of Native peoples, and interventions throughout Latin America, the promise of endless growth allowed Americans to defer reckoning with internal contradictions around race, class, and democracy. Grandin, a professor at Yale and author of acclaimed histories of Latin America, shows how expansion enabled a particular kind of freedom, one defined by the absence of social obligation rather than collective self-governance. The frontier allowed white men to escape the constraints of settled society, whether debts, marriages, or the compromises required by living among others. This understanding of freedom as escape rather than citizenship shaped American political culture. When the frontier closed, that expansionist energy turned inward in ugly ways, manifesting as nativism, border militarization, and eventually the politics represented by Donald Trump's wall. Grandin connects the vigilantes who patrolled the Mexican border in the early twentieth century to contemporary militia movements. He argues that the border wall represents not just a policy position but the endpoint of a particular American mythology. Readers interested in how historical narratives shape present politics will find this synthesis of western history, borderlands studies, and political analysis compelling and timely.