On the occasion of the book’s quasquicentennial, our special issue brings together four articles that show the continuing relevance of W. E. B. Du Bois’s The Philadelphia Negro: A Social Study (1899). The contributors illustrate how a fresh perspective on the theoretical insights that Du Bois began to develop in The Philadelphia Negro deepen understanding of contemporary topics such as gentrification, policing, residential mobility, and the rhythyms of daily life in Black neighborhoods. Taken together, these articles adopt four tenets of a Du Boisian Sociology that are grounded in the contributions of The Philadelphia Negro: (a) using history to contextualize the contemporary, (b) studying social phenomena through the subaltern perspective, (c) using a “case of” design, and (d) analyzing the structural context that shapes individual outcomes, with attention to people’s agency. As our special issue demonstrates, while already a classic, The Philadelphia Negro deserves an even wider audience for its lessons on what city blocks can tell us about the character of a city: the residents and their institutions that have come and gone, the shape of changing neighborhoods, and what all that could mean for urban change in the future.