This age fits with a Thomas Hall of Choctaw County. see census below
I have no idea of where Sources used by Historical Data Systems came up with his age at enlistment as 28, other than that being an extrapolation of his age 2 years later when he died, which his records only show his age at death as 30. No other reference to his age is listed in the records. The 30 could very well be the result of a translational error.
Correction to my initial post: Died of wounds RECEIVED 28 July at Atlanta
Notes on one card for Sergeant Hall:
"wounded July 28,1864, died age 30
Has a grave dug in the Erwin* Hospital, Barnesville, Ga.
[* Erwin not Gwen]
See statement Jas. Spratt, Co. D, 42nd Ala."
The only thing I find in his this file is that James Sprott, Company D, 42nd Alabama died June 10, 1864 at Erwin Hospital, Ga.
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1860 United States Federal Census about Thos M Hall
Name: Thos M Hall
Age in 1860: 36
Birth Year: abt 1824
Birthplace: South Carolina
Home in 1860: Desoto, Mississippi
Gender: Male
Post Office: Olive Branch
Household Members:
Name Age
Thos M Hall 36
S J Hall 36 F born in Alabama
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Here is one other record for a Thomas Hall.
Thomas Hall, Private, Company H, 28th Mississippi Cavalry was surrendered with his company at Citronelle, Alabama May 4, 1865, paroled at Gainesville, Alabama Jay 12, resident of Chocktaw [sic] County, Mississippi, no other records
28th Regiment, Mississippi Cavalry
28th Cavalry Regiment was formed during the spring of 1862. Some of the men were raised in Benton, Washington, Bolivar, Coahoma, and Tunica counties. In November the unit contained 32 officers and 563 men, then in January, 1862, its designation was changed to 2nd Confederate Infantry Regiment. Colonels John D. Martin and Edward F. McGehee, and Major Thomas H. Mangum were in command.
1860 United States Federal Census about Thomas Hall
Name: Thomas Hall
Age in 1860: 28
Birth Year: abt 1832
Birthplace: Georgia
Home in 1860: Township 21, Choctaw, Mississippi
Gender: Male
Post Office: Fame
Household Members:
Name Age
Thomas Hall 28 Farmer
Jane Hall 22