This article deals with specific traits of the development of ports on the Western coast of Flanders (Nieuwpoort, Dunkerque, Ostende, Gravelins, Lombardsijde, Mardyck) in the late fourteenth — early fifteenth centuries. The research of the documents reveals the profound impact on the life of these towns of their geographical position at the sea and land border of Flanders during the active periods of the Hundred Years’ War. Warfare led to serious destructions as well as made special measures to strengthen the defence of these towns necessary. The Anglo-French War also stimulated the flourishing of piracy that was one of the occupations of the population of Flemish ports despite the prohibition of piracy by the government. Most of these towns were situated on the trade routes that connected inner regions with the coast and the clothmaking cities and towns of Southern Flanders and Artois with the main centre of international trade, Bruges, via a system of rivers and canals. These proved to be an important positive factor for the development of some ports. Their citizens had the responsibility to maintain the security, proper condition, and work of these trade routes (to maintain the lighthouses along the coast, fix different problems with the canal system). The population of Flemish ports was mainly occupied in fishery. The analysis of the distribution of several extraordinary taxes voted by Four Members of Flanders makes it possible to reveal the financial abilities of ports of West Flanders. The author considers that the development of Nieuwpoort, with its various forms of economic and social life, differed in many ways from the development of smaller ports such as Gravelins, Lombardsijde, and Mardyck.