On Trinity Sunday, 1397, three kingdoms were crowned as one. In the Swedish border city of Kalmar, the political elites of Denmark, Norway, and Sweden gathered to anoint a single ruler over the entire Scandinavian north - and to sign two documents that said entirely different things about what that union was supposed to be. One was written on parchment, sealed by sixty-seven men, and promised a king by divine right. The other was written on paper, bore only ten partial seals, and promised something closer to a federation. Neither document prevailed. For a hundred and twenty-three years, the Kalmar Union tore itself apart along the fault line between them. Crown of the North tells the full story of the union's turbulent century: the plague-ravaged world that made it possible, the iron queen who built it from nothing, the miners of Dalarna who rose against its foreign bailiffs, the Norwegian Atlantic empire that dissolved into silence, and the judicial massacre in a Stockholm square that finally destroyed it. It is a story of constitutional genius and administrative catastrophe, of aristocratic intrigue and popular revolution, of a political experiment that came closer than it should have to working - and failed in ways whose consequences still shape the modern north.