The presence of the Sillon de Bretagne, however, causes some local variations in the climate, with marsh areas generally colder than the rest of the town.

Of this treasure, which belongs to the monetary deposits buried during the disorders of the years 270-275, the departmental Dobrée museum preserves 350 currencies of bronze and silver, the golden currency in the effigy of the "Gallic" emperor Postumus, the golden ring and the six of seven silver spoons today.

During the reign of Charlemagne; the territory was initially under the dominion of his nephew, Roland, who was given the title of 'Prefect of the Breton March'.

The following year, in the aftermath of the Battle of Jengland, the Breton March, with Nantes as its capital, was integrated into Brittany by the Treaty of Angers.

The subsequent eighty years, however, were made difficult by the constant infighting between the Breton warlords, who promoted Viking invasions.

From 919 to 937, the town was managed by the Vikings, who were defeated by Alain Barbe-Torte, the grandson of Alan the Great, the last king of Brittany.

Since the Germans could no longer conduct major submarine operations from the bases without a supply line, the SHAEF commander, U.S. General Dwight D. Eisenhower decided to simply bypass these ports, and the Allied armies focused their resources on the invasion of Germany.

Saint-Nazaire and the other two German "pockets" remained under Nazi control until the last day of the war in Europe, 8 May 1945.