He enrolled 20 August 1862 as a private in Company H, 7th Ohio Volunteer Infantry (Captain Samuel McClelland). He was wounded at the Battle of Chancellorsville and died in hospital at Washington, DC, on 17 May 1863. His wife received a widow's pension of $8 per month plus an additional $2 for her minor child Lucy E. Barnum. By the time of her death the monthly payment had increased to $12.
From the Western Reserve Chronicle, Warren. Ohio, May 27, 1863: Samuel H. Barnum, son of Hiram Barnum, Esq., of Braceville, Ohio died in the hospital at Washington, D.C. on the 22nd aged 25 years. Mr. Barnum first enlisted in Capt. Barrett’s company, 19th Regiment, O.V. in the three months’ service, and fought gallantly in the Battle of Rich Mountain, and all others in which his regiment was engaged. When the new regiments were being raised last summer, he received a recruiting commission as Lieutenant, conditioned upon his raising twenty-five men within ten days. He enlisted sixteen for the 7th Regiment, eight for the 19th and two for the 24th—twenty-six men in all, but because he had not enlisted them all for one regiment, he failed to receive his commission, although he had the highest recommendations, and at once enlisted with his sixteen men, at their request in the 7th. In the arduous campaign of the past winter in which the 7th Regiment bore no conspicuous and dangerous a part, he won the respect and esteem of his fellow soldiers by his kindness of heart, manliness and unflinching bravery. At the battle of Chancellorsville on the 2d inst., the 7th Regiment was lying to the front, near to and behind a ridge of land, and from that position, Capt. McClelland (who had command of the regiment) was unable to see where to direct his fire, and here they were lying for some time. At length Capt. McClelland called for three men out of Co. H to volunteer to ascertain where the enemy were. Samuel H. Barnum, William Hunter and David Wintersteen sprang forward and advanced upon the ridge. They had only advanced about two rods, when Hunter was shot through the wrist and Barnum through the side as he was retreating to his company — Wintersteen only remaining unhurt. The Regiment had 420 men on the march, most of them being in the fight, a few being on picket duty, and a few detailed for train guard; out of this number eighty-seven were killed, wounded or missing.
The remains of Mr. B. were brought home by his father, and the funeral took place at his residence in Braceville, on Sunday last, attended by a large concourse of people, who were addressed briefly and to the purpose by Colonel J. F. Asper and Mrs. Mercia Boynton Lane. He was buried with military honors, the Warren Firemen (of whom he was formerly a member) tendering their services on the occasion.
He leaves a widow—a daughter of Robert M. Miller, Esq. of this place and an infant daughter.