Returning to America, Du Bois taught briefly at Wilberforce University in Ohio, where his earnest dedication to scientific sociology had little room for expression. He then undertook a commission from the University of Pennsylvania to compile a study of the black community in Philadelphia. Despite discrimination and condescension from university faculty, Du Bois produced the monumental Philadelphia Negro -- the first scientific study of urban blacks in America.

The achievement of Du Bois' Philadelphia study was the beginning of his reputation as a sociologist. He accepted an offer from Atlanta University in 1897 to teach History and Economics. There, Du Bois planned a long-range series of studies dealing with the issues and problems that faced black Americans. The result was the Atlanta University Studies, which was one of the first continuous sociological surveys in the United States. Du Bois hoped that through scientific inquiry, the oppressive conditions of black Americans could be brought to world attention and that the shadows of racial prejudice could be dispelled by the light of reason. But after almost ten years of patient research, Du Bois was shocked into action by the Atlanta Riot of 1906. Disinterested scientific investigation was not enough. He began to see that direct social action was needed to counter the political and economic oppressions that stood in the way of black aspirations.