We study how employing organizations divide up the tasks they do, and therefore how they structure their employees’ jobs. Much research in the past three decades has shown that employing organizations’ job structures determine the social, economic, and psychological outcomes experienced by workers, and thus determine patterns of stratification and social mobility. Although much attention has been paid to the consequences of organizational job structures, little has been done to analyze their causes. Our analysis of job structures in U.S. wineries adds to the handful of causal studies on this topic. Building on sociological theory, we predict that technical factors – scale and scope of operations – increase the complexity of job structures, specifically the number of job titles, functions delineated by those titles, and people with multiple job titles. We further predict that cultural factors – organizational age, prevailing notions of what is “normal,” and organizational form – influence job structures. We find strong effects of both technical and cultural factors. We also find that these forces can conflict and complement each other, and that the identities embedded in organizational forms determine whether and how technical and cultural factors affect job structures.