Assimilation and split labor market dynamics are core foci in research on immigration, race/ethnicity, and inequality. Little work, however, systematically analyzes how assimilation and group-level power dynamics within labor markets intersect relative to employment trajectories and rewards. In this article, we do so by offering integrated analyses of racial/ethnic inequalities for an important ... [Show full abstract] case, New York City from 1910 to 1930. Our multi-method analyses draw from the Integrated Public Use Microdata Series (IPUMS) and content-coded coverage from the New York Times for the period. Quantitative and qualitative results demonstrate a clear racial/ethnic hierarchy as well as group-level variations in opportunity relative to industrial concentration, segregation, and discrimination. Assimilative attributes and generational status mattered, yet certain inequalities were more firmly entrenched. Most pronounced, as seen in our qualitative analyses, were processes of social closure, discrimination, and related exclusionary constraints-constraints encountered and eventually alleviated, to some degree, for new white ethnics but not for African Americans. We conclude by discussing the theoretical and empirical utility of considering the embedded nature of assimilation within broader contexts of racial/ethnic closure in labor market opportunities and also relative to historical and contemporary eras.