Gloria:

The 2 S.C. infnatry was not raised form Orangeburg District; it is possible that he was conscripted later in the war and assigned to the 2 S.C.

The 20 S.C. had a great many of its men drawn from Orangeburg. A number also spilled across the line into Lexington District. I would suggest that is a strong candidate for your David R. Knight.

The 2 S.C. Artillery had companies from all over the State, but I am of the impression that at least some of the men came from Orangeburg.

If you have not yet looked at their records in Compiled Service Records, I would suggest that you do so for each potential unit. The initial enlistment card often tells how far the man came to the rendezvous, and you can either eliminate or include the man based on that data. Furthermore, the CSR file may show that the man died or in some other way was not your target. Also, sometimes notations in the roll will give you his residence.

There is one additional source that may help. In the 1890's, in order to support the State pension for Confederate veterans, the State solicited rolls of companies be prepared by the veteransw. This was before CSR was available, so that making such a list was crucial. Because the rolls were often prepared from memory, they are commonly called the "Memory Rolls," but the actual title is "South Carolian Volunteers in Confederate Service", a three volume manuscript bound set held by the S.C. Department of Archives and History. If you have access to the Archives, you should consult SCVCS. The rolls commonly listed the county of residence. Anderson County Library has it on microfilm, and I think, so does the Greenville County Library. But you may be far from any of those places. Good luckj.