His own research is in European and American intellectual history, the history of science (particularly mathematics), and the intersection of history and computing. He is the co-author of Digital History: A Guide to Gathering, Preserving, and Presenting the Past on the Web (University of Pennsylvania Press, 2005), author of Equations from God: Pure Mathematics and Victorian Faith (Johns Hopkins University Press, 2007), and has published articles and book chapters on the history of mathematics and religion, the teaching of history, and the future of history in a digital age in journals such as the Journal of American History, the Chronicle of Higher Education, and Rethinking History. Dan is an inaugural recipient of the American Council of Learned Societies' Digital Innovation Fellowship.