The 8th Illinois Infantry Regiment Company "A" (3month)
http://www.civilwar.ilgenweb.net/r050/008-3a-in.htm
List John Bowen from Decatur muster in 25 April, 1861 and mustered out 25 July, 1861.

The 8th Illinois Infantry Regiment Company "A" (3 year)
They organized 25 July, 1861 - 4 May, 1866.
http://www.civilwar.ilgenweb.net/r050/008-a-in.htm

On this roster his residence and date of muster are not listed, rank of recruit. The remarks say he was transferred to Hopkins Batt'y Co C 2d Art. I can find no other enlisted or officers that were transferred to Hopkins Artillery. Is/was this a valid unit, if so to what state were they from?
The following is the only other mention I can find about the Hopkins Artillery, even this I am assuming that it is the same as that associated with the 8th Illinois 6 years later:
"January 1857 Governor-elect Bissell and family arrived for installation to office and was escorted by Capt. Hopkins' artillery. From "A Complete History of Illinois from 1863 to 1873" written by Alexander Davidson and Bernard Stuve 1877." This was found on a Google search.

I am trying to get information on John Bowen so I can ask for his records for the whole story. He was supposedly killed during the siege of Vicksburg. I find it interesting that there is such absence of the Hopkins's Artillery in any records. He is not listed in the cemetery for that battle and I can only guess that he was one of those that could not be identified when transferred following the war. John’s brother Daniel Bowen fought with him in another Illinois unit 116th Company “A” and he survived, Daniel was my
G-Grandfather.

Any information on this unit (Hopkins’ Artillery) would be greatly appreciated also any suggestion.

Thanks
Pat