Marshall originally thought he was going to be an English professor, and he taught at Penn, the University of New Hampshire and La Salle College until he was hired by Farm Journal to help create a centennial-celebrating keepsake publication. His later writing credits include The New York Times Magazine, Philadelphia Magazine, Boston Magazine and many periodicals that now are merely remembered, sometimes even fondly, such as the Philadelphia Inquirer Magazine.
Marshall and his wife, Martha, collaborated to write and produce Dear Old Penn in Postcards: The University of Pennsylvania, 1900-1923, which won three CASE awards. And he worked with David Y. Cooper III, M.D., on Innovation and Tradition at the University of Pennsylvania School of Medicine: An Anecdotal Journey (University of Pennsylvania Press).
Marshall earned a B.A. from Dartmouth College, an M.A. from Penn State, and a Ph.D. from the University of California at Berkeley. He lives in Philadelphia with Martha, who also writes. Their children are now far-flung: Daughter Kate is author of the 2009 novel Remedies, and son Gabriel is an emergency physician and creator of the short film, The Rest of My Life: Stories of Trauma Survivors. Marshall's hobbies include cooking, Spanish language study, tai chi, Argentine tango, watercolor painting and drawing.