William A. Forristall was born on August 4, 1830, in Pittsfield, Massachusetts, to James and Jane Forristall. The family moved to New York in the late 1830s before settling in Cincinnati, Ohio, by the 1850s. His father died sometime before 1860. By 1860, Forristall was working as a painter in Cincinnati and living with his mother and siblings. He enlisted in the Union army on April 20, 1861, and mustered in as a private in Company I of the 6th Ohio Infantry. He mustered out on June 18, 1861, when his term of enlistment expired, but he returned to federal service when the 6th Ohio reorganized as a 3-year regiment soon afterward.
Confederate forces captured him near Cheat Mountain, West Virginia, on September 11, 1861. They sent him to Richmond, Virginia, and then Tuscaloosa, Alabama. Writing from Tuscaloosa in December 1861, he noted that he was “Discouraged and awful hungry” and “Terrible low spirited.” He and his fellow prisoners had only “Rotton Rice & Black Beans & Grease Water” to sustain themselves. Confederates released him on parole on March 13, 1862, and he “arrived safe at Home” in Cincinnati that June. He was discharged on October 23, 1862.
Forristal rejoined the Union army on May 2, 1864, and mustered in as a private in Company H of the 137th Ohio Infantry eight days later. The regiment performed garrison duty around Baltimore, Maryland, and he mustered out on August 19, 1864. He returned to his family’s home in Cincinnati after leaving the army and resumed his work as a sign painter. By 1870, he owned $200 of personal property. He married a woman named Mary sometime in the 1870s. He applied for a federal pension in June 1880 but never received one. He died of a bowel ailment in Cincinnati on August 1, 1882.