Twentieth-century circumpolar epidemics shaped historical interpretations of disease in European imperialism in the Americas and beyond. In this revisionist history of epidemic disease as experienced by northern peoples, Liza Piper illuminates the ecological, spatial, and colonial relationships that allowed diseases – influenza, measles, and tuberculosis in particular – to flourish between 1860 and 1940 along the Mackenzie and Yukon rivers. Making detailed use of Indigenous oral histories alongside English and French language archives and emphasising environmental alongside social and cultural factors, When Disease Came to this Country shows how colonial ideas about northern Indigenous immunity to disease were rooted in the racialized structures of colonialism that transformed northern Indigenous lives and lands, and shaped mid-twentieth century biomedical research.