Salt is essential for life, and “salt road” – the routes for the transportation of salt – have existed since prehistoric times. It was also a key preservative before refrigeration. The expansion of Europe’s North Atlantic fisheries in the late Medieval period increased the demand for salt.
Salt was an important trade commodity. The Setúbal deposit near Lisbon in Portugal was regarded as the best in Europe. Another major deposit was at Aveiro, 70km south of Porto. The trade in salt became a royal monopoly in Portugal in 1576. A simplified description of the international trade follows: Dutch ships came to Portugal and paid for salt using silver. They sold the salt in the Baltic, and brought wheat back to the Netherlands, some of which was also sold in Portugal.
Spain exported salt from Sanlucar de Barrameda and the Puerto de Santa Maria, near Jerez in the bay of Cadiz.
Amsterdam played a key role in the salt market. Often a ship would deliver a load (for example, grain) to one port in Portugal, and then pick up a load of salt for the return journey.
An important use of salt was for salting fish. Sweden was an important importer of Portuguese salt. Iberian salt was even exported to Russia.