Francis Marion National Forest has MILES of well-graded, usually gravel Forest Service Roads. You can ride 20 or 30 miles on some sections without crossing pavement. It's a great place to spend a day exploring. Even the paved roads in the area are decent- nice scenery and some curvy sections, although nothing like real twisties.
The Wambaugh off-road trail is supposedly very gnarly and suitable for serious off-road bikes only.
2007 Buell XB12X Ulysses
1983 Honda VT500FT Ascot