The factories were established from 1356 onwards in the main trading centers, usually ports or central hubs that have prospered under the influence of the Hanseatic League and its guilds and kontors. The Hanseatic cities had their own law system and furnished their own protection and mutual aid. The Hanseatic League maintained factories, among others, in England (Boston, King's Lynn), Norway (Tønsberg) and Finland (Åbo). Later, cities like Bruges and Antwerp actively tried to take over the monopoly of trade from the Hansa, inviting foreign merchants to join in.