He was 35 years old when he enlisted (2, 5). He was born in Tyrone County, Ireland (2).
He was a laborer when he was enlisted (2, 5).
He was 5 feet 6-1/4 inches tall, had a light complexion, grey eyes, and light hair (2 [5'6-1/4", light complexion, grey eyes, light hair], 5 [5'6-1/2", dark complexion, grey eyes, light hair]).
He enlisted and was mustered into service for three years in company E on 21 August 1861, at Philadelphia Pennsylvania (1, 2, 5, 7). He was enlisted by Captain Lentz, and mustered into service by Colonel Reiff (2, 5).
He was transferred on 28 December 1861 to company G, because company E was over the maximum number of men (1, 2, 3).
He was discharged on 12 June 1862 on surgeon's certificate of disability, at the regimental hospital in Alexandria, Virginia (1, 2, 4, 5, 7).
On 7 November 1864, he applied unsuccessfully for a pension (6, 7).
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 descriptive roll, company E, entry 53
3 register of men transferred, company E, entry 1
4 company G, register of men discharged, #9 (Henry McKnight)
5 company G, descriptive roll, entry 52 (Henry McKnight)
6 pension index, by name (Henry McKnight)
7 pension index, by regiment, 91st PA Infantry, company G (Henry McKnight)
[I did not find an entry for him in the index on <www.ancestry.com> to the 1890 veteran's census (searched May 2007)]