Hiram N. Hamilton was born around 1837 in Cecil County, Maryland, to Hugh and Sarah Hamilton. His father was a weaver who owned $200 of real estate by 1850. He grew up and attended school in Cecil County, and by 1860, he was working as a carpenter.
He enlisted in the Union army on August 20, 1862, and he mustered in as a private in Company G of the 6th Maryland Infantry. According to his service records, he was 5 feet, 11 inches tall, with light hair and blue eyes. He eventually earned a promotion to corporal. He died of typhoid fever in Washington, D.C., on August 17, 1863.