Thomas J. Criswell was born around 1843 in Maryland to Nicholas and Mary Criswell. His father was a farmer and rail engineer who owned $200 of personal property by 1860. The family lived in Howard, Maryland, until the 1850s, when they moved to Barnesville, Ohio. His mother probably died in the early 1850s.
Criswell enlisted in the Union army on July 22, 1861, and he mustered in as a private in Company H of the 20th Indiana Infantry later that day. The regiment took part in the Peninsula campaign, the Second Battle of Bull Run, the Battle of Chancellorsville, and the Battle of Gettysburg. He eventually earned a promotion to corporal. He died at Gettysburg on July 2, 1863.