Jane Addams is well known for her leadership in urban reform, social settlements, pacifism, social work, and women's suffrage.The men of the Chicago School are well known for their leadership in founding sociology and the study of urban life.What has remained hidden however, is that Jane Addams played a pivotal role in the development of sociology and worked closely with the male faculty at the Department of Sociology at the University of Chicago. By using extensive archival material, Mary Jo Deegan is the first to document Addams's sociological significance and the existence of a sexual division of labor during the founding years of the discipline. As the leader of the women's network, Addams was able to bridge these two spheres of work and knowledge.Through an analysis of the changing relations between the male and female networks, Deegan shows that the Chicago men varied widely in their understanding and acceptance of her sociological though and action.Despite this variation, it was through her work with the men of the Chicago School that Addams left a legacy for sociology as a way of thinking, an area of study, and a methodological approach to data collecting. This previously unexamined heritage of American sociology will be of value to anyone interested in the history of the social sciences, especially sociology and social work, the development of American social thought, the role of professional women, the Progressive Era, and the intellectual contributions of Jane Addams.