The Hanseatic League was an association (Hansa) of north German cities for the promotion of trade. Formed at Lubeck in 1158, other Baltic ports joined the League and after 1201, when Cologne became a member, many of the Rhineland cities also joined. In 1253 the Laws of Lubeck were accepted by Hamburg and other member cities as the basis of mercantile law.
In addition to member cities, there were outlying agencies called Kontore which enjoyed extra-territorial rights at such trading centers as Bergen, Novgorod, Boston, Lynn, London, and Bruges. In London the traders were called Merchants of the Steelyard, from the old German Stalgaard, meaning a place for the exhibition of goods. Portraits of such merchants give a good indication of their wealth and social status. But because they dominated the trade of the Baltic and the Low Countries their monopoly aroused jealousy. The League possessed no central defense organization, so that it was easy to withdraw its privileges when the nation state began to develop. Its influence was further diminished by the movement of the herring shoals from fishing grounds in southern Sweden to the North Sea. About 1630, when the Dutch had captured the northern trade, the Hanseatic League ceased to exist.
At the height of the power of the League at the end of the fifteenth century it controlled 60,000 tons of shipping. Trade was carried on chiefly by sea in order to escape vexatious tolls and political barriers; but this entailed danger from pirates or wrecks, all the more so because Hanseatic captains seem to have been slow to adopt the compass and chart, which by that time were in common use in the Mediterranean.
This expansion of trade necessitated the building of bigger ships, for which the Baltic was well equipped. For centuries, contruction materials such as Danzig plank, Riga masts, and Stockholm tar were essential to the maritime powers of the west. The principle trading vessels of the Hanseatic League were the single-masted cog and hulk, which developed into the three-masted caravel and carrack, usually of about 400 tons. The cogs were carvel-built (i.e. with the planks laid edge to edge), instead of overlapping as in Norse clinkerbuilt ships. The construction of the hulk thus leads the way for the caravel, with its three distinct sections -- the towering fore and aft castles with a deep waist between them.
Mutual arrangements were made for pilotage, lighthouses and so on, but as the League did not possess a specific naval force its fleets were vulnerable, especially in the English Channel. Nevertheless this free association of some 160 towns was something unique in economic history and in their time the Hansa enjoyed almost a complete monopoly of trade in northern Europe.