A pathbreaking study of why, paradoxically, workforce specialization and job responsibilities have increased hand in hand. In the United States and other late-industrial countries, the division of labor has changed radically over the last 150 years. This comes as no surprise: the nature of work has been transformed by new technologies, new discoveries, and new challenges. While the fact of change was predictable, the type of change is not at all as theorists envisioned. For all their differences, Adam Smith, Karl Marx, Emile Durkheim, and Max Weber each presumed that specialized workers would perform a narrower range of tasks. The early history of the industrial age supported this view. As the assembly line overtook the workshop, the artisan who constructed every part of a useful object was replaced with workers who handled a single piece of the work process. The Division of Rationalized Labor demonstrates that—although early industrialization may have operated as Smith, Marx, and