I had initially been under the impression Soldiers Ground would be graves for South Carolinians only. Most likely because of the years the dead were buried here.

That is not true. Many of the stones list the unit served and home state. There are also northern troops, though not many, in the surrounding areas.
Found on a walk.
Note; yes that is a confederate battle flag, banned in most places, especially South Carolina. Because this is private property I do see some. However, most flags here are the old State flags.