Theory, capable of probing into the shifting perceptions of immigration and tenement poverty that thanks to Riis's work gained a foothold across America. This sweeping change was an epistemic event sparked by the publication of How the Other Half Lives in 1890. In this seminal book, and in countless reform publications and illustrated lectures, Riis presented the Other Half as a destitute population to be otherwise perceived, understood and helped toward prosperity.

Riis's primary contributions to the reform movement was the establishment of a new charity object: the truth about the Other Half. Petersson raises original questions about its unveiling and proposes an alternative mode of inquiry as well a reorientation of empirical research. The Making of The Other Half pays particular attention to the surge of reform movements in Copenhagen during Riis's residence in the city prior to his emigration to America.

The discursive migration that took place along with Riss's journey from Copenhagen to New York is crucial for understanding the subsequent mutation event. By recognizing this parallel migration, a new history of Riis's work is revealed, and a new dimension of the Other Half opens up.