After retiring from a four-decade career in medicine, Lowry — assisted by a new wife, Beverly — shifted in the 1990s to writing non-fiction historical works. He has authored or co-authored more than 20 books in this field, the majority dealing with the American Civil War period. Much of the Lowrys' research was carried out at the U.S. National Archives in Washington, D.C., where, over the course of a decade, the Lowrys compiled a large index of thousands of previously uncatalogued Civil War documents. Lowry's first and best-known book on this subject, "The Story the Soldiers Wouldn't Tell" (1994), received a favorable review in "The New York Times" as "the first study of sexual behavior associated with the Civil War," and was praised in "Esquire" as "amusing and fascinating." Two subsequent works on Civil War courts-martial, "Tarnished Eagles" (1998) and "Tarnished Scalpels" (2000; co-authored with Jack D. Welsh), were well-reviewed in "Civil War Times" and "Kirkus Reviews", respectively. Lowry has occasionally published on other historic events, such as the Battle of Taranto and the sinking of the "Titanic". His 2004 book on the Lewis and Clark Expedition earned him an award from the Lewis and Clark Trail Heritage Foundation.