Ken,
Thank you for the information, that is more detail than I had on their service. Green and Hartwell had Confederate veteran emblems added to their graves some time later, and I found them on a list of veterans from Falls County. It is interesting that you found his name as Green E. Stillwell, I knew that he went by Green but my father recalled that the family referred to him as E.G., which made me think that Green was his middle name. He was named after his father's brother whose first name was Green.
The information I have on them is rather slim but I hope to be able to do more research soon.