What happened to shared historical experiences in the discursive processes of constitutional reform in Sweden and Finland? This article examines the use of 18th-century history in early 20th-century politics. Building on a long-term survey of Swedish and Finnish estate and parliamentary debates, it analyses the political implications of differing national historiographies in the two successor states of the 18th-century Swedish realm, focusing on how the ancient past and collective (and often selective) memories of the Age of Absolutism, the Age of Liberty and the Gustavian Age were used by parliamentarians in constitutional debates. The analysis demonstrates how the Finnish polity continued to be profoundly influenced by these 18th-century constitutions even after the Russian Revolution, while Sweden took the post-French Revolution constitution of 1809 as its point of departure. In both countries, interpretations of the long 18th century were ideologically motivated in an age of the parliamentarization of government and the democratization of the representative system. This leads us to a discussion of the history-political significance of the common and differing understandings of representative government in the two interconnected countries.