The Atlantic world in the late nineteenth and early twentieth centuries was a space of contradiction and hope. From New York to Havana to Buenos Aires, ‘Spreading Rebellion’ documents the activities of migrant laborers from Spain who contributed to the genesis, development, and consolidation of maritime unionism. The rise of steamships in the late nineteenth century brought a massive increase in global transport, along with a ballooning international workforce. Coexistence onboard through shared working and living conditions contributed to solidarity among seafarers, while power exercised through their mobility helped stimulate the process of organizing dockworkers on land. Alonso and Struthers focus keenly on how this multilingual and multiracial workforce imbued their movement with an anticapitalist ethos. These dynamics animated aggressive campaigns for legislative reforms, and fights for workplace control with unions such as the Industrial Workers of the World. ‘Spreading Rebellion’ is, above all, a transnational history that moves away from statist frames of reference.