St. Clair Drake (1911-1990) and Horace R. Cayton (1903-1970) Black Metropolis: A Study of Negro Life in a Northern City.New York: Harcourt, Brace and Company, 1945.
Urban sociology, a field that developed in the early twentieth century, was centrally concerned with mapping cities, especially the demographic, economic, and racial makeup of urban centers. Drake and Cayton, pioneers in the study of Black urban life in the early twentieth-century, elaborated on the concept of urban zones, which you can see here as concentric circles. Drake and Cayton were primarily concerned with the "Black Belt," the wide black swathe visible near the city's center. Many African Americans lived in the area, a result in part of racist housing practices and attitudes, twentieth-century industrialization, and the Great Migration of Blacks from the South to Northern urban centers such as Chicago.