

According to John H. Goodale, author of History of Hillsborough County, New Hampshire (Philadelphia: JW Lewis & Co., 1885) page 182, "In the battle of Drury's Bluff, May 13, 1864, while making an advance on Richmond, this regiment bore the "brunt" of the contest. Major James F. Randlett, now captain of a cavalry company in the regular army, was wounded. Adjutant Elbridge J. Copp, who, entering the service as a private at seventeen, had won promotion, was also wounded. On the 16th of August a fierce engagement took place at Deep Bottom, at which Adjutant E.J. Copp was severely wounded, which compelled him, in October following, to return to Nashua." An obit from 1887, for his father gives us a shade more info about his war service and the years after "Mr. Joseph Copp, a prominent citizen of Nashua, NH, died recently at 86. He left a married daughter and five sons, among the latter being Rev. H.B. Copp, Capt. C.D. Copp and Col. E.J. Copp, the last-named in command of the Second Regiment of the State National Guard."
I'm going to assume that Mr. Copp was not yet in business at the outbreak of the war, being 17 years old. However, it doesn't seem like he waited long after the war. An insurance report from a fire in Nashua in April 1870 records a slight loss at "C. D. & E. J. Copp, books, etc."

Being in the book business, Elbridge Copp's own contribution came to light in 1911. One bookseller describes Reminiscences of the War of the Rebellion 1861-1865. "Copp claimed to be the youngest commissioned officer in the Union Army during the war. This Scarce reminiscence of the 3rd NH volunteers is nicely done with numerous maps, illustrations and photos of members of the Regiment." One offering also includes this information "Long inscription by the author's widow: "Colonel Copp fought his last great battle, with his usual bravery and fortitude, in the summer of 1923, responding to the "roll call" on high on August 3rd, taps were sounded on August 6th." So, if we presume he was 17 in 1861, he would have been about 79 in 1923.
