We merge data on spatial variation in the presence of convicts across eighteenth and nineteenth century Australia with results from the country's 2017 poll on same-sex marriage and with household survey data. These combined data allow us to identify the lasting impact of convict colonization on social norms about marriage. We find that in areas with higher historical convict concentrations, more Australians recently voted in favor of same-sex marriage and hold liberal views about marriage more generally. Our results highlight how founder populations can have lasting effects on locally held social norms.