Home guard
According to Thomas Walter, the 13th ward home guard was a predecessor. Since he says 'of our organization', it's not completely clear whether he means of Company A or of the whole 91st PA. It may be relevant that Eli Sellers, of company G, served as captain of a Home Guard unit.
On 19 April 1861, the City Councils suggested that each ward form a Home Guard, and Colonel Augustus J Pleasonton was named commander on the 20th. Most wards formed Home Guard units, spurred by local businessmen. [J Matthew Gallman, Mastering wartime: a social history of Philadelphia during the Civil War (Cambridge: Cambridge University Press, 1990), pages 16-17; see also Winnifred K Mackay, 'Philadelphia during the Civil War, 1861-1865' (Pennsylvania magazine of history and biography, pp.3-51, at pp.13-14)]. The Philadelphia City Archives has material on the Home Guard, 1862-1863, in group 60.1, Annual Message and Reports of Departments, which might have further interesting information. [John Daly, Descriptive inventory of the archives of the city and county of Philadelphia, Philadelphia, 1970]
By 29 April 1861, the Thirteenth Ward had organized one company, and was more than halfway to organizing two others. Edgar Gregory was elected Captain of the first company (the "juniors") by acclamation. ['Local intelligence: Home Guard', Philadelphia Inquirer, 29 April 1861, page 2; 'Local intelligence', Philadelphia Inquirer 4 May 1861 page 2]
In June 1861, Gregory and John M Bickel ran for election as Colonel of the Home Guard. Results published in the Inquirer have Bickel winning 408 to 297 votes. ['Home Guard elections' Philadelphia Inquirer 26 June 1861 page 8]
The Home Guard, including the Thirteenth Ward Home Guard, took part in a Fourth of July parade in 1861. ['Local intelligence', Philadelphia Inquirer 5 July 1861 page 8]
When he formed the 91st, Gregory apparently brought with him from the Thirteenth Ward Home Guard his first lieutenant (Frank Gilbert), his second lieutenant (Ansel Hamburg), and his first corporal (Randolph M Smith, initially a first sergeant, later promoted to second lieutenant)). Also, John Lentz was captain and David H Lentz was second lieutenant of the Ellsworth Guard, from the first ward; B J Tayman was first sergeant of the Sixth Ward Home Guard; Peter Keyser was fourth lieutenant of the Young Guard (from the twelfth ward), and Eli Sellers was captain of the Putnam Guards (from the Twentieth Ward). ['The Home Guard organization', Philadelphia Inquirer, 29 June 1861, page 2]
On 7 August 1861, Brigadier General Pleasonton promised to release men from the Home Guard unconditionally if they wanted to volunteer for active service. On the same day, Gregory claimed six companies were already connected with the regiment, and invited other company commanders to join. [source: 'The Philadelphia Home Guard Regiment' and 'Head-quarters Home Guard', Philadelphia Inquirer, 13 August 1861, page 5; see also 'Colonel Gregory's regiment', Philadelphia Inquirer 26 August 1861 page 8]
Wallace's regiment
On 20 August 1861, the War Department authorized Edward Wallace to form an infantry regiment. By 29 August 1861, he was recruiting, with George Todd as lieutenant colonel. They were at Camp Edwards, which was on Islington Lane, opposite Odd Fellows' Cemetery.
Sometime betwen 4 and 19 October 1861, this regiment was consolidated with Colonel Gregory's regiment.
Sources: Bates, [page 186]; 'Attention, Captain of companies Philadelphia Inquirer, 29 August 1861, page 5 (also 28 Aug 1861 page 5); 'Captains and others commanding companies' Philadelphia Inquirer, 31 August 1861, page 5, also 2 September page 5; 'The Wallace Regiment', Philadelphia Inquirer, 5 September 1861, page 5 (also 6 September page 5); 'Col. Wallace's Regiment' Philadelphia Inquirer 4 October 1861 page 8; 'Camp Chase at Gray's Ferry' Philadelphia Inquirer 19 October 1861 page 8
Fire departments
Thomas Walter also identifies two other squads in company A, one as the "Fishtowners", or "Shad Hose" fellows", and another as the "Ringgold Hose" gang. William Redheffer has received information from the Philadelphia Fire Museum that explains this. The 'Shads' was a nickname for Kensington Hose Company #30, which also used the name "Fishtowners"; twenty of its members volunteered for service during the Civil War. Ringgold Hose Company had thirteen members volunteer for service during the Civil War. (These were volunteer companies, and few names of members survive.)
Church
Many members of the Kensington Methodist Episcopal Church were in the regiment (e-mail, 9 and 24 June 2001, Claire Labenz, citing Annals of Kensington Methodist Episcopal Church, by Swindal). While this may have been a coincidence, perhaps groups volunteered from the church.
Status in August 1861
At a meeting on 19 August 1861, reporting the status of regiments in training, Edgar Gregory reported that his regiment comprised seven incomplete companies, two of which were to be mustered in on the 20th, and that the regiment could be ready to march in two weeks. [see 'Important military movements', Philadelphia Inquirer 20 August 1861 pages 1 and 8]