Distinguishing 'Hoover' from 'Hooven' is often hard; I have tentatively assigned records to William T Hooven and William Hoover largely based on the presence or absence of the middle initial.
He was 42 years old when he was enlisted (5). He was born in Philadelphia, Pennsylvania (5).
He was 5 feet 9 inches tall, and had a dark complexion, hazel eyes, and brown hair (5). His nose was broken (5).
He was enlisted and mustered into service on 23 August 1861 (1, 5). He was enlisted for three years, at Philadelphia, Pennsylvania, by Colonel Reiff (5). He served as a private in company C (1).
He was wounded on 3 May 1863 at Chancellorsville, Virginia (1). On 7 May 1863, he was reported missing in action (2). On 17 May 1863, he was reported to be in the Corps Hospital as a paroled prisoner (3).
On 4 November 1863, he was detailed as a stretcher bearer in the ambulance corps (4).
He reenlisted as a veteran volunteer (1).
He may have returned to duty from Brigade Headquarters on 2 May 1864 (7).
He was absent, sick, when the regiment mustered out (1).
On 2 December 1864, his widow, Louisa Hoover, applied successfully for a pension (8, 9).
In 1890, his widow, Louisa Hoover, was living in Springfield, Delaware County, Pennsylvania (post office Norton) (10).
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) (William Hoover)
2 consolidated morning report, 91st PA, 7 May 1863 (Private Hoover [?])
3 consolidated morning report, 91st PA, 17 May 1863 (Private Hoover [?])
4 consolidated morning report, 91st PA, 4 November 1863 (Priv W Hoover [??]) (uncertain id)
5 company C, descriptive roll, entry 44 (William Hooven ['n' is clear])
6 company C, untitled list, probably of status at muster out, entry 36 (William Hooven ['n' is clear])
7 consolidated morning report, 91st Pennsylvania, 2 May 1864 (Hoover [uncertain ID])
8 pension index, by regiment, 91st PA Infantry, company C (William Hoover)
9 pension index, by name (William Hoover)
10 1890 US census, veterans' schedule, Pennsylvania, Delaware County, Springfield, supervisor's district X [sc. 2], enumeration district [39], page 1 [sic, sc. 2 (William Hoover)