Since arriving at USD in 1988, Lehmann has organized the annual Student History Conference for the northern plains region.
Close to 100 undergraduate and graduate students from colleges and universities within a 150-mile radius attend the Student History Conference at USD to present and evaluate papers.
Lehmann earned his bachelor's degree from Augustana College in Sioux Falls, his master's degree from the University of Maryland and his PhD from the University of Chicago. Lehmann teaches Western Civilization, ancient and medieval history, and the history of the Renaissance and Reformation. His research includes archaeological excavation at Caesarea in Israel. He has published book reviews and articles about Greek history, Roman and late Roman epigraphy.