A salt road refers to any of the prehistoric and historical trade routes by which essential salt was transported to regions that lacked it. From the Bronze Age fixed transhumance routes appeared, like the Ligurian drailles that linked the maritime Liguria with the alpages, long before any purposely-constructed roadways formed the overland routes by which salt-rich provinces supplied salt-starved ones.
The salt highways of Europe were the navigable rivers, where by medieval times shipments of salt coming upstream passed rafts and log-trains of timber, which could only be shipped downstream. And even along Europe's coasts, once long-distance trade was revived in the 11th century, the hot and sunny south naturally outproduced the wet north. By the Late Middle Ages the expanding fishing fleets of the Low Countries required more salt than could be produced locally; the balance was made up with salt from the Iberian Peninsula: "The United Provinces could have been brought to their knees if their supplies of salt had been blocked at the end of the sixteenth century. Spain did no more than dream of this," Fernand Braudel has written. In Ming China, salt as well as rice was shipped from south to north, along the Imperial Canal as far as Beijing.
Salterns and saltpans
In France, a major source of marine salt with access to expansive hinterlands in need of it was the wetlands region in Languedoc called the Camargue; from the salt pans called salines, convoys of boatloads of salt could be carried up the Rhone to Seyssel where it had to be off-loaded and carried by mule train inland to the little village of Regonfle near Geneva, where it rejoined a waterway. Of the early modern period in Europe, Fernand Braudel remarked that in spite of the flux and reflux of economics:
"no salt mine was ever abandoned and the scale of the equipment needed put these mines in the hands of merchants from very early days. Salt-marshes on the other hand, were exploited by artisanal methods: the merchants took control only of transport and marketing, both in Setúbal in Portugal and in Peccais in Languedoc. Salt marketing was probably quite big business along the Atlantic seabord or the Rhône valley."
The vast interior of Poland was salt-starved, its maritime districts lying under rainy skies and fronting the Baltic Sea. By medieval times the process of mining for fossil salt supplemented the age-old techniques of evaporating sea salt in tidal pans. By the 14th century, at Wieliczka near Kraków, Braudel reports that peasant extraction of salt from brine evaporated in large shallow iron pans had been eliminated by the early industrialisation of salt mining. "Galleries and shafts were now dug to a depth of 300 metres, and enormous winches powered by teams of horses brought blocks of salt to the surface. At its peak, production stood at 40,000 tons a year and the mines employed 3,000 workers. By 1368, the cooperation of the Polish state had been obtained."