These are Colonel Henry Fowler (left) and two other officers, unidentified, in a wartime photograph at the Library of Congress. Lieutenant Colonel Henry T Fowler led the 63rd New York Infantry, part of the famous Irish Brigade, at Antietam, where he was wounded in the arm.

This photograph of Colonel Charles W Roberts is in the collection of Civil War Photographs at the Library of Congress. Roberts commanded the 2nd Maine Infantry on the Maryland Campaign.

Lieutenant Colonel Joseph H Barnes led the 29th Massachusetts Infantry, part of the Irish Brigade, in their assault on the Sunken Lane at Antietam. His photograph is from a carte-de-visite (CDV) sold on ebay in 2016.

Colonel James McQuade commanded the 14th New York Infantry at Antietam. This photograph is in the Library of Congress.

This postwar photograph is of Henry Lawrence Eustis, professor of engineering at Harvard’s Lawrence Scientific School (now School of Engineering and Applied Sciences – SEAS) from 1849 to 1862, and from 1864 to 1885. It’s online thanks to SEAS.

A graduate of Harvard (1838) and first in his class at West Point (1842), Colonel Eustis commanded the 10th Massachusetts Infantry on the Maryland Campaign.