This article investigates how sociodemographic, economic, medical, and public health factors influence infant mortality by using data about German administrative areas from 1871 to 1933. Marital fertility has the largest impact on infant mortality, followed by illegitimacy, medical care, urbanization, and infant welfare centers. The variables considered here account for most of the variation in infant mortality. Some of the unexplained variance is due to factors associated with regions, such as breastfeeding patterns, and with time periods, such as national health insurance. The analyses found no evidence that advances in medical technology affected infant mortality or that the influence of economic development changed over time.