The analysis of the evolution of the location of economic activity in Portugal between 1890 and 1980 depicts a strong concentration of productive activity in the coastal regions. We estimate data for regional GDP per capita, which show that the evolution of regional inequality followed an inverted U-curve, in line with that observed in other regions of Europe, but with a rather late peak, in 1970. The reasons for this behaviour may be found in the limits to industrialisation in the interior regions and the benefits generated by the agglomeration economies in the more developed coastal regions.