His research focuses on the social and political history of race in America. His first book, White on Arrival: Italians, Race, Color, and Power in Chicago, 1890–1945 (2003), won the OAH Frederick Jackson Turner Award; as a dissertation, it won the Society of American Historians' Allan Nevins Prize. Guglielmo's current book project examines America's World War II military as a crucial and forgotten site of race-making and civil rights organizing. Pieces of this latest project have appeared as articles in the Journal of American History and the American Journal of Sociology. Guglielmo has received fellowships from the Charles Warren Center for Studies in American History at Harvard University and from the Research Institute of Comparative Studies in Race and Ethnicity at Stanford University.