Models of port development have hitherto concentrated on landward communications and the organization of maritime space in their explanation of changes in port location and activity. This study demonstrates that the level of economic development in hinterlands together with industrial and marine technology are also significant factors and indeed play leading roles in the process of port evolution. For a deeper understanding of the process of port evolution the case of Upper Norrland's ports has been investigated. An analysis of changes in port distri­bution since 1750 reveals two main processes: dispersion followed by concen­tration. The growth in the number of ports and loading places prior to 1885 was not regular but stepwise, with two rapid increases related to the relax­ation of mercantile restrictions, laissez-faire policies and the diffusion of new industrial activities. The fall in port numbers also corresponds to industrial changes and large-scale rationalizations of industry and transport systems have taken place in association with the economic changes following the two World Wars. The innovation and subsequent decline of new types of forest-based industries appear as a series of waves when their numbers are graphed. Charcoal ironworks, fine-blade water-driven sawmills, steam-powered saws, pulp mills, wallboard factories and paper mills demonstrate the succession of industrial and technological innovations. Clearly, the demand for the products of these industries, their shipping requirements and the physical needs and economics of contemporary transport have been the dominant factors in Upper Norrland's port development. On the basis of these changes, the evolution of the region's port system has been synthesized into the Upper Norrland model. Land communications have nevertheless had an important part to play in sus­taining port dominance at the mouths of the major river valleys, which have acted as corridors of penetration. This investigation shows that these gate­way ports had achieved significance long before the maximum number of scat­tered ports was reached, and it is doubtful whether the situation of a scattering of ports all of a similar status ever existed in reality. Early port dominance was sustained by later transport developments on land and in particular at sea, as river mouths provided the best sites for the construc­tion of outports and deep-water terminals. The long-term seaward migration of port activity and facilities has taken place and the Bottenhamn model demonstrates this process at the local level. The study concludes by putting the Upper Norrland and Bottenhamn models into a wider context. The world-wide influence of colonial powers and maritime nations has led to a diffusion of marine technology, and shipping require­ments must therefore have, prompted similar port developments throughout the world. / digitalisering@umu