This article presents an account of the spread and intensification of socio-economic links between a rural hinterland and the expanding city of Lae, Papua New Guinea (PNG), since the early twentieth century. Long-term ethnographic research in the Wampar area of the Markham Valley, close to Lae, has shown how variable the pace, intensity and extent of change in relations between an urban centre and its neighbouring hinterland can be. Based on fieldwork in the Wampar settlements and the village of Gabsongkeg, the article describes the role of novel socio-economic forms (mission stations, commodity production, markets, mining projects) and transport infrastructure (airstrips, highways) in processes of differential peri-urbanisation. The specific location and circumstances of the introduction of these forms has had the effect of differentiating a social field that previously lacked significant social contrasts, positioning settlements and groups in relation to state and international institutions in ways that have impacted on social reproduction under colonial and post-colonial conditions. The article also discusses the role of people’s expectations in the creation and exploitation of economic opportunities that have the potential to entrench existing socio-economic inequalities further. Not surprisingly, the ethnography suggests that the size of the areas of land and capital investments entailed in novel economic activities has had decisive socio-economic effects locally. This suggests therefore that the large-scale capital-intensive projects being proposed in the region are already reconfiguring regional social fields. Nevertheless, the specificities of space, time and sequencing of developments are proving crucial to the manner in which events are unfolding, placing significant demands on the ethnographic analysis of concrete cases.