The song plays a prominent role in Michael Shaara's American Civil War historical novel The Killer Angels and its film adaptation Gettysburg. Confederate Brigadier General Lewis A. Armistead recalls a dinner at the marital home of his best friend—the now-Union Major General Winfield Scott Hancock—at the U.S. Army garrison in Los Angeles, California in 1861 (at which time Armistead was a major and Hancock a captain), and that the song was sung there that night. This was the night before Armistead and several other Southern officers were to depart for the Confederacy, having resigned their US Army commissions. Armistead and Confederate Brigadier General Richard B. Garnett—who was also present at the dinner—go on to be killed and Hancock to be severely wounded as Armistead's and Garnett's brigades assault the position defended by Hancock's II Corps on Cemetery Ridge in Gettysburg during Pickett's Charge. During Gettysburg, "Kathleen Mavourneen" is sung once by an Irish tenor at the Confederate campThe subtitles for the DVD mistakenly call the song "Captain Mavourneen". and thereafter is used frequently as a theme in Randy Edelman's musical score for the film.
