Historical studies suggest that nineteenth- and twentieth-century processes of national integration in the countries of Western Europe fundamentally changed interactions between individuals living in different parts of those countries. These studies, however, were rarely able to provide direct evidence for this process due to a lack of sources. This chapter uses the distances between birthplaces of spouses, as indicated in marriage certificates collected by the GENLIAS database for five Netherlands provinces (1812–1922), to measure increasing spatial interaction and widening geographic horizons. Various descriptive measures of the change in distances between spouses and in directional preferences are presented, as is analysis of the changing relationship between social position and geographic horizon. Results of spatial analysis demonstrate that the geographic horizons of young men and women in the Netherlands started to increase at the end of the nineteenth century. There were large disparities between provinces and strong differences in the geographic horizon of grooms from various social classes, with the higher social classes having wider horizons. Implications of these outcomes for the study of the development of family structure, technology and infrastructure and, more generally, for the extent and timing of modernization and national integration in nineteenth-century Netherlands are discussed.