Tuberculosis was the most devastating infectious disease of the 20th century. Spread initially in the nineteenth-century fur trade, tuberculosis rose in intensity after 1900, with its greatest impacts in the 1920s and 1930s. This chapter shows the prevalence of tuberculosis infection, its interaction with other pathogens, and the impacts of tuberculosis on children and young adults especially, including how the residential school system amplified the epidemic in the North. More than any other disease, tuberculosis changed Indigenous relationships with the land. The colonial state belatedly responded to this epidemic, relocating the sick to institutions in southern Canada. This policy of medical relocations became emblematic of Northern health history and colonialism in the decades to come.