At the turn of the twentieth century, the white slavery panic pervaded American politics, influencing the creation of the FBI, the enactment of immigration law, and the content of international treaties. At the core of this controversy was the maintenance of white national space. In this comprehensive account of the Progressive Era’s sex trafficking rhetoric, Leslie Harris demonstrates the centrality of white womanhood, as a symbolic construct, to the structure of national space and belonging. Introducing the framework of the mobile imagination to read across different scales of the controversy—ranging from local to transnational—she establishes how the imaginative possibilities of mobility within public controversy work to constitute belonging in national space.