S.C. Code § 4-3-500
Union County is bounded as follows: on the north by the Pacolet River which separates it from Cherokee County; on the east by Broad River which separates it from York, Chester and Fairfield Counties; on the northwest by Spartanburg County from which it is divided by a line, beginning at the corner of Cherokee and Union Counties with Spartanburg County on the Pacolet River, and running thence S. 33.75° W. to the intersection of Fair Forest Creek; thence S. 6.5° W. across the Tyger River to Hackett's Creek; thence S. 17° W. 2 miles and 28 chains to the Cross Keys road; thence S. 12° W. to a dead Spanish oak on the north bank of the Enoree River, a little above Nusgrove's Ford, opposite Gordon's Mill; on the southwest by Laurens and Newberry Counties, from which it is divided by the Enoree River, down to Avery's Ford; thence by the road to Crenshaw's Ford, on the Tyger River; thence down said river to its junction with the Broad River, which forms its southeast boundary.
S.C. Code § 4-3-500