This article presents a micro-historical study of two 20th-century ironworks in Sweden and Finland, examining local social structures and their dynamics. By analysing ethnographic data available on these ironworks, it is argued that the boundaries that the contemporaries observed inside the community followed occupational lines. These were based on tangible factors such as spatial issues and living standards and on general issues related to identity, all of which depended on work and occupation. Changes caused by modernization and industrialization in these tangible factors were reflected in local social structures, which helps us to understand the dynamics of both local social structures and these large processes.