What The project aims to describe and analyse the historical epidemiology of malaria in Denmark between 1660 and 1860. Despite today being associated with subtropical regions, malaria was an endemic and common disease in Europe as far north as Scandinavia until the early twentieth century. Even in northern Europe, it was a serious co-morbidity in low-lying marsh parishes, which were kept in a demographic check with high mortality. Medical historians have in the past focused on epidemic diseases like cholera, plague and pandemic influenza, and malaria has for a large part been overlooked. For this reason, there are large gaps in our knowledge about northern European malaria. The few studies about it are moreover situated in different countries and centuries. This leaves us with a fragmented historical overview and no comprehensive answers to the very pungent questions about its counterintuitive existence. By studying malaria over a period of 200 years, my project traces the disease over several centuries to write one comprehensive history of malaria in Denmark. Why Malaria disappeared seemingly without deliberate anti-malarial interventions. Before its demise, it had seemingly begun a lethality decline, which began in the late eighteenth century. This decline took place around the start of the great mortality decline that would come to characterize European demography up until today. Understanding the mechanisms behind malaria's lethality decline can provide cues to how this epidemiological transition took place in the often-understudied historical rural societies. Moreover, with the current climate change, malaria threatens to return to northern Europe. Outbreaks have already occurred and with migration, the encroachment of other vector borne diseases from the Mediterranean region, and anti-malarial drug resistance, new outbreaks can occur. In addition to describing an overlooked disease, this project also contributes to both the historical demography of Europe and our understanding of modern malaria epidemiology. How The project is structured into two parts. Part one explores the roles of malaria as an acute cause of death and co-morbidity. Using the signature features of malaria - i.e. the epidemiological dynamics characteristic of malaria - I explore whether marshland areas had larger consistent mortality burdens than elevated areas. Here, I also explore whether climatic influences such as warm summers and storm surges led to high mortality in the spring where malaria epidemics took place. In the second part, I explore possible environmental and social dynamics that could have led to a decline in malaria mortality. I focus on the roles of agricultural improvements in the late eighteenth and early nineteenth century as well as the effects of embankments and drainage in areas with brackish marshlands.