[en] During the 19th century, Denmark experienced rapid urban population growth amidst deficient sanitary conditions. This study explores the changes in the country’s life expectancy from 1850 to 1910 for both the total population and the urban and rural areas, using vital statistics data on deaths. It also examines the contributions by causes of death to the changes in life expectancy in Copenhagen. This analysis shows that in Denmark a new mortality regime began to take shape in the 1890s, marking the passage from relatively slow gains in life expectancy and fluctuating mortality to rapid and sustained improvement, especially in cities. Until the 1880s, such gains were driven mainly by mortality reductions among children aged 1–4. From the 1890s, reductions in infant mortality contributed significantly to further gains. Reductions in mortality from a few (mainly infectious) diseases were responsible for most of the gains observed in Copenhagen. Although declining, the urban–rural gap in life expectancy persisted throughout the period, particularly for men.