Thank you for the link and the info. My ggreatgrandgather was free and from his papers he said he enlisted because he thought he was going to be conscripted. I have no picture of him so I do not know his color. I do have a picture of his son ( my greatgrandfather) and know that in general he and his children were very light. I am stuck trying to understand why he was imprisoned and not set free. When the prisoners were offered freedom from Rock Island, he joined the Union and fought for them.
I am reading a book on the prison and hope to dredge up a regimental history. He was associated with the light artillery so I am assuming that he pushed the heavy guns around and assisted in handling the firing supplies.