Blyth Harbour. Photo by Harry Rowland, 1975.

There has been a harbour at Blyth since the medieval period, but until the 17th century there were only a few landing places for ships carrying coal and salt. Until the early 19th century the harbour at Seaton Sluice was much more important. However, in the 19th century the harbour greatly increased in size and more docks and piers were built. The main cargo was coal from the nearby coalmines. In the 20th century the importance of the dock declined, though it is still used.