This article examines social heterogamy as an indicator of “societal openness”, by which is meant the extent to which social origin, as defined by the social position of one's parents, is used as the main criterion for selection of a marriage partner. We focus on two topics. The role first of migration and then of occupational identity in this selection of a partner according to social origin. And in order to evaluate the true social and economic context in which spouses lived, we do not use a nationwide sample but rather choose to examine marriage certificates from eleven cities and villages in Belgium, both Flemish and Walloon, during the nineteenth century. By observing different patterns of homogamy according to social origin we show in this article that partner selection was affected by the relationship between migration, occupational identity and class structure. It seems difficult to interpret all these divergent patterns in terms of modernization. In our opinion the historical context creates a complicated set of conditions reflected in differences in the type and strength of migration and in the sectoral composition and evolution of the local economy. The whole exerts an influence over partner selection.