Vignetted studio bust portrait albumen CDV. Washington, D.C. and New York: Brady & Co.’s National Photographic Portrait Galleries, [ca. 1864-5]. Photographer’s imprint to mount verso. Two-cent blue Washington proprietary revenue stamp to mount verso. Research pencil identifications to mount verso read: "Bvt Brig Gen Martin T. McMahon / MoH — 6-30-62."

This sharp study from the legendary studios of Mathew Brady captures Martin T. McMahon, a prominent staff officer whose leadership was central to the operations of the 6th Corps. Posed in an officer’s frock coat with his lieutenant colonel’s shoulder straps visible, McMahon prominently wears a Greek Cross — the proud insignia of the 6th Corps — pinned to his breast. The reverse of the mount features a clear Brady backmark and a blue revenue stamp, placing the sitting in the final years of the conflict.

McMahon earned the Medal of Honor for his "extraordinary heroism" during the Battle of White Oak Swamp, Virginia, on 30 June 1862. During the chaotic retreat of the Seven Days Battles, McMahon was serving as an aide-de-camp. Under a heavy and concentrated fire, he voluntarily braved the wreckage of a destroyed bridge to destroy valuable Union property and documents before they could fall into Confederate hands. His actions, performed at great personal risk while the rear guard was being pressed, prevented a significant intelligence disaster for the Army of the Potomac.

Following his heroism on the Peninsula, McMahon’s rise was meteoric. He served as the assistant adjutant general for the 6th Corps, becoming a trusted confidant to Gen. John Sedgwick. He was present at Sedgwick's side when the general was killed at Spotsylvania, and he continued to lead with distinction through the Siege of Petersburg. He finished the war with the brevet rank of major general of Volunteers.

[Civil War, Union, Confederate] [Photography, Early Photography, Historic Photography, Daguerreotypes, Ambrotypes, Tintypes, Cased Images, Union Cases, Albumen Photographs, CDVs, Carte de Visites, Cartes de Visite, Carte-de-visite, Cartes-de-visite, CDV, Cabinet Cards, Stereoviews, Stereocards] 

The image is in generally excellent condition, featuring strong tonal contrast and sharp detail in the subject’s features and corps badge. The albumen surface is well-preserved with minimal age-related toning. The mount remains structurally sound with clean edges and a bold photographer’s backmark. The 2-cent revenue stamp on the reverse remains firmly affixed, and the research identifications provide definitive provenance for this 6th Corps hero.