S.C. Code Ann. § 4-3-340

Lancaster County is bounded as follows: on the north by the North Carolina line; on the west by the Catawba River and Big Sugar Creek from the point where it enters said river to intersection of the North Carolina line, which separates it from the counties of York, Chester and Fairfield; on the south by Kershaw County from which it is divided by the line mentioned in Section 4-3-330 and on the east by Chesterfield County, from which it is separated by Lynch's River.