This article traces the spatial history of New York City's geographic school subdistrict boundaries throughout the 20th century, exploring the historical relationship between race, space, and schooling in New York City and beyond. It seeks to both make the case for studying the spatial history of within-district education boundaries and put the results of our historical mapping project into the public domain. Ultimately, we hope that researchers will use our data to explore their own questions about the history of New York City, its neighborhoods, and its schools, and that some may embark on similar boundary-mapping projects for other cities, counties, and school systems.