This study analyses social heterogamy in western and southern Finland during the early stages of industrialisation, from 1700 to 1910. Marriage patterns are examined by comparing the social classes of spouses' parents, which can be understood as the social origin of the spouse. The rate of heterogamy within the freeholder class was only 19.8%, whereas it was 71.1% in the upper classes, 59.7% in the tenant class and 76.5% in the labour class. In addition, only roughly 20-30% of grooms whose fathers were landowners married brides from lower social classes. Certain individual-and family-level characteristics increased the odds of a heterogamous marriage: remarrying, age difference, being an illegitimate child or a single mother, and the first marriages of those in the labour class. Regarding macro-level variables, we found that higher rates of emigration and poor-relief recipients, along with having a larger Finnish-speaking population, led to higher levels of heterogamy. Other issues increasing the odds of heterogamy included living in the more urbanised or industrialised regions and moving to different regions. This study identified strict marriage patterns, which did not significantly change with respect to heterogamy. Nevertheless, indications exist that industrialisation and urbanisation began eroding the prevailing traditions.