Opening on 18 February 1918 at the Shubert Theatre, the four-act drama by Augustus Thomas ran for 120 performances. The action of the first two acts takes place during the Civil War , and the remainder 40 years later. The title refers to the central character, played by Lionel Barrymore, who is believed to have been a Southern-sympathizing pacifist—a Copperhead—when his country was at war. In the stirringly poignant finale, he finally breaks his silence and shows a letter from his friend Abraham Lincoln who had asked him to infiltrate the Copperheads in service to the Union cause. Although the three-hour play tested the patience of audiences, the climax—when an old Union soldier took off his Union blue jacket and hat to put them on the long-despised Copperhead—always elicited tears followed by fervently patriotic ovations.
The Historical Dictionary of the American Theater. James Fisher.