This talk explores a crisis in the sanctuary ideal as a fundamental approach to US immigration policy and the United States’ role in the world. Nineteenth-century Americans took very seriously the idea that the United States, as an emerging republic in a world of powerful monarchies, had a duty to offer safety to those escaping political repression elsewhere: if America wanted the distinction of being an exemplary and exceptional republic, Americans must hold open their doors for the persecuted. According to this ideal, refugees fighting for their homelands’ freedom could keep their torches alight in America, mobilizing fellow exiles, financial resources, and public opinion to advance their causes worldwide; Americans would promote the global advance of liberty precisely by serving as a welcoming harbor for the persecuted. The United States was and ought to be an “asylum for the oppressed of all nations.” The ideal always had sharp racial limits; Asians need not apply. But it helped bring aspiring nationalists to US shores—from Hungary, from Ireland, from Cuba—where they were often celebrated. The ideal, and the policies that flowed from it, came under intense challenge in the late 19th century in the face of rising labor mobilization and radical activism. Haymarket was, in many respects, a pivot: a moment of shock which turned the tide of US immigration politics away from the sanctuary ideal and towards a more anxious set of preoccupations about the preservation of the industrial order and immigrants as potentially existential threats to American society. In discussing this moment, the paper will reflect more broadly on continuity and change in US immigration politics and culture, and the role of sudden, unanticipated events in altering the terms and terrain of debate.