Henry Duncan was born around 1829. He was living in Ohio by the early 1860s. He enlisted in the Union army on November 2, 1861, and mustered in as a private in Company E of the 48th Ohio Infantry on December 7. He probably took part in the Battle of Shiloh in April 1862. He fell ill soon afterwards, and army officials sent him to a general hospital on April 10. He received a month-long furlough on April 17, but he failed to return. A provost marshal in Ohio finally arrested him on October 23, 1863, and sent him back to his regiment. He died of “chronic diarrhea” in New Orleans, Louisiana, on April 3, 1864.