He was born in 1829/30 (8 (32 in 1862)). He was born in Ireland (8).
When he enlisted, he was a labo[rer] (8).
When he enlisted, he was 5 feet 9 inches tall, and had a light complexion, grey eyes, and dark hair (8).
He was enlisted for three years, on 24 April 1862, at Alexandria, Virginia, by First Lieutenant Black (8). He was mustered into service as a private in company H on 27 or 29 April 1862, at Alexandria, Virginia, by Lieutenant G Black (1, 8 , 13, 14).
On 10 March 1863, he was dropped from the regiment as a deserter (3). (Oddly, he doesn't seem to have been reported as absent without leave before that!) On 24 April 1863, he was reported returned (4).
William Reiff later noted that "[a]n acquired desire to spree at time caused Mac, or Hughey, as we called him, to leave the different hospitals and have what he considered a 'good time' of it before going to the front" from hospital (12).
In May 1863, he was apparently wounded in the head (10, 11 [head]).
On 24 August 1863, the Fifth Corp Provost Marshall sent a letter to the regiment, about McLaughlin's being forwarded under guard (5). On 25 August 1863, he returned to the regiment from being absent sick (6).
On 30 December 1863, Sinex reported that he was one of 30 men who had more than fifteen months to serve who were willing to reenlist (2; 1 has him reenlisted as a vet). On 2 January 1864, he was transferred to the 155th Pennsylvania Infantry, while those eligible were on veterans' leave (7).
At some point in 1864, a paymaster refused to pay him 'on account of his hospital record' (presumably, because of his record of desertion) (12). McLaughlin allegedly went to the White House, pushed his way inside, and pled his case to Lincoln, who ordered the paymaster to pay him (12).
He was absent when the regiment mustered out (1). He was a private, in company H (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 letter, Sinex to Marvin, 30 December 1863
3 consolidated morning report, 91st PA, 10 March 1863 (Hugh McLaughlin)
4 consolidated morning report, 91st PA, 24 April 1863 (Hugh McLaughlin)
5 letter received, 24 August 1863, from Captain Ryder, Provost Marshall 5th Corps (Hugh McLaughlin)
6 consolidated morning report, 91st PA, 25 August 63 (Hugh McLaughlin)
7 consolidated morning report, 91st PA, 2 January 1864 (McLaughlin)
8 company H, descriptive list, #104 (Hugh McLaughlin)
9 'The Ninety-first Pennsylvania volunteers', Philadelphia Inquirer 8 June 1864 page 3 (Hugh McLaughlin)
10 'The ninety-first Pennsylvania volunteers', Philadelphia Press, Wednesday 13 May 1863, page 2 (Hugh McLaughlin)
11 'The Ninety-first Pennsylvania at Chancellorville', Philadelphia Inquirer 13 May 1863, page 8 (Hugh McLaughlin)
13 index to compiled service records of volunteer Union soldiers who served in organizations from the state of Pennsylvania (Hugh McLoughlan)
14 index to compiled service records of volunteer Union soldiers who served in organizations from the state of Pennsylvania (Hugh McLaughlin)