He is a co-director of the Drexel Engineering Cities Initiative. Knowles is editor and co-author of Imagining Philadelphia: Edmund Bacon and the Future of the City (2009, U Penn Press), and is author of the forthcoming book Disaster City: Risk Experts in the American Metropolis. He teaches courses in modern United States history, urban history, and the history of technology. Knowles received his Ph.D. in 2003 from the Johns Hopkins University, Department of the History of Science, Medicine, and Technology.