This paper examines conceptual change in negotiating borders in the European North. By analyzing the definitions of the status given to Finland in peace treaties between Russia and Sweden, the paper strives to enlighten how through the centuries Russia was involved in negotiating key concepts of European political language, state, territoriality and nationality. With the theoretical discussions in conceptual history as starting point, the paper illustrates how a concept of state, separated from the person of the ruler, emerges in mediaeval and early modern peace treaties, and how the estates of the ruler gradually gain status as political units. With special focus on how notions of a linear state border were attached to the territory of Finland, the paper discusses broader processes of the development of ideas of territorial state and linear state borders. The paper asks how and at which political junctures new understandings of sovereignty appear in the treaties between Russia and Sweden and how international recognition of territorial integrity and the rights of citizens were introduced as part of the relations between the two countries. The broader aim of the paper is to contribute to a comparative discussion on how state-making and bordering processes in the European North were linked to political modernization, and how and to what degree the redefinition of borders and territories were connected to new kinds of conceptualizations of state, sovereignty and nationality characteristic to modern politics.