John H. Hancock, a sergeant in Company H, 29th Massachusetts Infantry of the Union Army during the American Civil War, was born ca. 1841 in Massachusetts. While employed as a clerk, Hancock enlisted as a private at Charlestown, Massachusetts, in a unit that would be designated as Company H, 29th Massachusetts Infantry and join the remainder of the regiment already deployed on the Virginia Pensinsula. Hancock was promoted to corporal on August 3, 1862, and to sergeant on March 15, 1863. Wounded, he was discharged from the service on August 25, 1864. Returning to Massachusetts, Hancock married later that year. Together with his wife, Annie, Hancock resided in Chelsea, Massachusetts, and was employed as a custom house inspector. The couple had several children (including Lucy B., Elizabeth, Annie, Herbert and Edgar W.). John H. Hancock died on September 9, 1913.

The 29th Massachusetts Infantry was organized at Newport News, Virginia, in December 1861, combining the existing 1st Battalion Massachusetts Infantry with three new companies (including Company H) organized in the Suffolk County, Massachusetts area. The regiment remained on the Virginia Peninsula until the end of August, participating in battles at Fair Oaks and Malvern Hill. With the failure of the Peninsula Campaign, the 29th withdrew to Washington, D.C., where it assisted in covering the retreat from the second battle of Bull Run, then joined in the advance into Maryland. The regiment saw heavy losses at the Battle of Antietam. During the fall and winter of 1862, the 29th remained in the northern Virginia area. In the spring, it was transferred westward and participated in the siege of Vicksburg and the capture of Jackson, Mississippi. The regiment spent the fall and winter in eastern Tennessee, participating in the battle of Campbell's Station, then was transferred to eastern Virginia, where it took part in the Wilderness Campaign and the siege of Petersburg. After the fall of Petersburg and Richmond, the regiment returned to northern Virginia. It was mustered out of service on July 29, 1865.