Although some scholars treat racial residential segregation in Northern cities as a twentieth-century phenomenon, recent research on New York and Chicago has shown that black-white segregation was already high and rising by 1880. We draw on data from the Philadelphia Social History Project and other new sources to study trends in this city as far back as 1850 and extending to 1900, a time when DuBois had completed his epic study of The Philadelphia Negro. Segregation of "free Negroes" in Philadelphia was high even before the Civil War but did not increase as the total and black populations grew through 1900. Geocoded information from the full-count data from the 1880 Census makes it possible to map the spatial configuration of black residents in fine detail. At the scale of the street segment, segregation in that year was extraordinarily high, reflecting a micro-pattern in which many blacks lived in alleys and short streets. Although there was considerable class variation in the black community, higher status black households lived in areas that were little different in racial and class composition than lower status households.