A Danish fortified town at the narrowest point of the Øresund, whose keep Kärnan controlled the strait, and where Christopher of Bavaria died childless in January 1448.
Helsingborg stands on the Scanian shore of the Øresund, at the point where the sound narrows to about four kilometres and the Danish islands come closest to the Swedish mainland. Permanent settlement here is documented from 21 May 1085, and for the whole of the Middle Ages this was a Danish town — Scania did not become Swedish until the Treaty of Roskilde in 1658.
Everything about the place follows from the geography. The narrowest crossing of the sound was the hinge between the two halves of the Danish kingdom and the gate through which all Baltic shipping had to pass, and whoever held both shores could tax the sea.
Denmark held both sides of the strait, Helsingborg on the east and Helsingør on the west, and that double grip was worth more to the Danish crown than any province. It made the sound a toll gate: from 1429 Eric of Pomerania levied the Sound Dues on every trading vessel that passed between the two towns, a charge that became the single largest source of royal income and remained so for centuries.
The same position made the town a target. Under the Treaty of Stralsund in 1370, which ended Valdemar IV’s war with the Hanseatic League, Helsingborg and the Scanian herring-market towns were handed to the Hansa for fifteen years — the League taking the castle that controlled the strait as the concrete guarantee of its trading privileges.
The keep known as Kärnan — "the core" — is the surviving fragment of the medieval castle. Danish legend credited it to a mythical king, but dendrochronology has settled the question: it was built in the 1310s, in the reign of Eric VI Menved. It is a square brick tower, the strongpoint at the centre of a much larger fortress whose walls and ranges enclosed the ridge above the harbour.
The castle’s military life ended with the Danish period. Sweden took it under the Treaty of Roskilde in 1658, Denmark retook it in 1676 during the Scanian War, and it returned to Sweden by the Treaty of Lund in 1679, after which Charles XI ordered most of the fortress demolished — it was too exposed, too close to Denmark, and too useful to an enemy. Only the keep was left standing.
The tower was given to the city in 1741 and restored in 1893-94 at the expense of the businessman Oscar Trapp, with Alfred Hellerström as architect, in an attempt to return it to a medieval appearance. It is open to the public and remains the symbol of the city.
Christopher of Bavaria was the one man elected to all three Scandinavian thrones in succession — Denmark in April 1440, Sweden in 1441, Norway in 1442 — and he took the union seriously enough to style himself archirex, arch-king, on the argument that he ruled an empire rather than three countries. He made Copenhagen the permanent Danish capital in 1443 and married Dorothea of Brandenburg in 1445.
His reign was short and hungry. Famine during it earned him the name of the Bark King, from the ground bark people mixed into what flour they had, and the Swedish nobility never stopped regarding him as a German import. He died suddenly at Helsingborg on 5 or 6 January 1448 — the sources differ over the day — aged thirty-one, with no child, and was buried at Roskilde Cathedral.
The consequence was immediate. With no heir and no agreed procedure, Denmark elected Christian I of Oldenburg and Sweden elected Karl Knutsson, and the Kalmar Union split into competing monarchies. A single unexpected death in a castle on the sound undid fifty years of dynastic arithmetic.
The medieval town lay on two levels — the castle on the ridge and the harbour and market below it — a division still legible in the street pattern, and its parish church of St Mary stands in the lower town. Its trade was the herring of the sound and the traffic passing through it.
After 1658 Helsingborg became a Swedish border town facing a Danish coast four kilometres away, which is how it has remained. For the archive its significance is Danish: a keep, a toll, and a royal death that broke a union.