Background/Context: In the first half of the 20th century, American policy makers at all levels of government, alongside housing and real estate industry figures, crafted mechanisms of racial exclusion that helped to segregate metropolitan residential landscapes. Although educators and historians have recognized the long-term consequences of these policies for the making of educational segregation, they have not yet fully perceived how strongly ideas about public schools mattered in the shaping of these exclusionary practices. Purpose/Objective/Research Question/Focus of Study: This historical study examines the "neighborhood unit" concept, its origins, and its influence, to illustrate the centrality of schooling in shaping mechanisms of racial segregation. The "neighborhood unit" concept, advocated during the 1920s by planner Clarence Perry before becoming central to local-level planning as well as federal-level housing policy, imagined self-contained communities within cities. Each of the units featured multi-purpose school-community facilities at their literal spatial as well as conceptual center. Perry and the influential cadre of planners who adopted the concept thought it would make metropolitan areas more livable, vibrant, and socially cohesive. But their neighborhood unit idea also encouraged racial segregation, in both schools and residential areas. Research Design: Sources for this qualitative historical investigation include published and unpublished primary sources from individuals, organizations, and government entities involved in making and using the idea of the neighborhood unit as well as extant historical scholarship. Conclusions/Recommendations: The history of the neighborhood unit shows that ideas about schools were central in the creation of the modern metropolitan landscape and enduring patterns of racial segregation. This evidence furthers the growing historical interpretation that housing segregation and school segregation operate not as separate terrain, but in deep connection with one another. By acknowledging and incorporating this historical perspective, educators and policy makers can reconceptualize segregation's roots, and perhaps its remedies.