He was 19 years old when he enlisted in 1861 (12). He was born in Philadelphia, Pennsylvania (12).
He was a dentist [?] (12).
He was 5 feet 7 inches tall, and had a light complexion, blue eyes, and light hair (12).
He enlisted and was mustered into service on 20 August 1861 as a corporal in company A (1, 11, 12, 13). He was enlisted for three years, at Philadelphia, Pennsylvania, by Captain Starr (12). (The list of non-commissioned officers (11) also claims he was "promoted from the ranks", which seems inconsistent with its claim that he was appointed corporal on 20 August.)
He is probably the 'Gordon' who went absent without leave with Thomas Walter in mid-June 1862 to visit Mount Vernon (2).
He was wounded--shot through the upper part of his leg--on 13 December 1862 at Fredericksburg, Virginia (1, 3, 4).
On 2 April 1863, he returned to the regiment from being absent sick (6). He had been furloughed from the hospital (6).
On 9 June 1863, he was sick in the Corps Hospital (7).
Because of his injury, he couldn't keep up with the regiment, and arrived late at Gettysburg. When he couldn't find the regiment, he reported for hospital service to the corps hospital, where he met and cared for Thomas Walter and others (4).
He fought at the Battle of Gettysburg (15). On 2 July 1863, he was missing in action (10). On 9 July 1863, he was dropped from the rolls, by order of Brigadier General Garrard (10). On the next consolidated morning report, dated 28 July 1863, he was reported as having been dropped because he was missing in the campaign (8).
He was transferred on 1 September 1863 to the Veterans' Reserve Corps (1, 12, 13). He was a sergeant when he was transferred (1), and was replaced as third sergeant by James Simpson (5). He served in E 3 of the Veterans' Reserve Corps (13).
On 4 October 1863, he was reported regained from missing in campaign, and transferred to the Veterans' reserve corps (9).
On 22 September 1881 (or 1882), he applied successfully from Pennsylvania for a pension (13, 14).
He died on 7 March 1928 (13).
Margaret L Gordon, his widow, applied successfully from Washington DC for a pension on 10 March 1928 (13, 14).
1 Bates, Samuel Penniman. History of Pennsylvania volunteers, 1861-5. Harrisburg: B. Singerly, state printer, 1869-71. 5 volumes. 'Ninety-first regiment', volume 3, pages 186-233. (In the roster)
2 Thomas Walter. 'Personal recollections and experiences of an obscure soldier'. Grand Army Scout and Soldiers' Mail volume 3 number 35 page 2.
3 Thomas Walter. 'Personal recollections and experiences of an obscure soldier'. Grand Army Scout and Soldiers' Mail volume 3 number 38 page 2
4 Thomas Walter. 'Personal recollections and experiences of an obscure soldier'. Grand Army Scout and Soldiers' Mail volume 3 number 40 page 1
5 special order 99, HQ 91st PA, 1 October 1863
6 consolidated morning report, 91st PA, 2 April 1863 (Sergt Gordan)
7 consolidated morning report, 91st PA, 9 June 1863 (Sergt Gordon)
8 consolidated morning report, 91st PA, 28 July 1863 (Sergt Gordon)
9 consolidated morning report, 91st PA, 4 October 1863 (Sergt Gordon)
10 Register of men discharged, co.A (James M Gordon)
11 register of non-commissioned officers, co.A (James M Gordan)
12 company A descriptive roll, entry 93 (James Gordon)
13 pension index, by regiment (James M Gordon)
14 pension index by name (James M Gordon)
15 Pennsylvania Memorial, Gettysburg, Pennsylvania (James M Gordon)
I did not find him in the index on <www.ancestry.com> to the 1890 veterans' census (searched October 2005)