My ancestor, Robert Duke, is on the memorial for William McGarrah's land grant on Crooked Creek, Camden District (now Lancaster Co.) SC. The SC Archives has his name spelled "McGurragh," and Robert Duke as Robert 'Duck."
Crooked Creek is a branch of Camp Creek and Dry Creek of the Catawba River, and lies on the eastern side of the river, above the town of Great Falls. The Duke, McGarrah, Rogers, Nelson, and other families were immediate neighbors there, and later the Thomas Mackey (and son Solomon Mackey) family was as well. Wm. McGarrah's son, James, is also listed.
The information that I have gathered seems to indicate that most of these families possibly/probably moved down from Augusta Co., VA in the 1760's - 1770's, and may very well have been living in the Scots-Irish Settlement there. (See: Lyman Chalkley's Chronicles of the Scots-Irish Settlement in Augusta VA).