John T. Gannaway was born around 1842 in Virginia. By 1860, he was a student in Smyth County, Virginia. He sided with the Confederacy during the Civil War, and he received a commission as a 2nd lieutenant in the 50th Virginia Infantry on May 1, 1864. Union forces captured him on May 12, 1864, after the Battle of Spotsylvania Court House. He died on March 10, 1865, in Fort Pulaski, Georgia.