The Civil War era's debates over citizenship are conventionally understood as having revolved around the status of emancipated African Americans. But they were also rooted in decades of US policy with regard to Native Americans. In Indian Country, citizenship's intended purpose was to dissolve Native political sovereignty and to make Indian lands available for sale to white settlers. These two histories of citizenship existed in dynamic tension and were occasionally forced together, as in the Civil Rights Act of 1866 and the Fourteenth Amendment. This essay traces Civil War–era policymakers' parallel debates over African American and Native American citizenship. Exploring those debates in particular through the thinking of conservative Democrat Allen Thurman suggests that while white supremacy came under sustained attack during this era, settler-colonialism—the ideology and practice of replacing Native with settler populations—did not.