James Clarke was born around 1837 to Samuel Clarke. He was probably born in Ireland. The family immigrated to America around 1845 and settled in New York. By the early 1860s, he was probably living in Ohio.
He enlisted in the Union army on June 19, 1861, and he mustered in as a corporal in Company D of the 5th Ohio Infantry. The regiment took part in the Battle of Antietam, the Battle of Chancellorsville, the Battle of Gettysburg, the Battle of Missionary Ridge, and the Battle of Kennesaw Mountain. He was promoted to sergeant in April 1863 and then to 1st lieutenant in May 1863.
In July 1863, he denounced northern Peace Democrats for inciting the New York City draft riots. "I think that New York copperheadism has worked its own destruction," he wrote. "King Horatio [Seymour] and King Jeff [Davis] can go down hand in hand to the domain of the first secessionist [the devil] on which there is no blockade and where brimstone and not cotton is King." He mustered out on July 8, 1864, and he died sometime afterward.