John S. Fiske was born around 1839 in Lowell, Massachusetts, to Sewell and Caroline Fiske. His father died around 1843. Fiske grew up and attended school in North Chelsea, Massachusetts, before beginning work as a trader. He enlisted in the Union army on August 7, 1862, and mustered in as a private in Company C of the 13th Massachusetts Infantry two days later. The regiment took part in the Battle of Antietam, the Battle of Fredericksburg, the Battle of Chancellorsville, and the Battle of Gettysburg. Fiske was killed at Gettysburg on July 1, 1863.