S.C. Code Ann. § 57-5-70: Highway transfers to the state highway system.

A county or municipality and the department may by mutual consent agree to transfer a road from the county or municipal road system to the state highway system. The transfer may be of the road "as is", without further improvement to the road or upon such terms and conditions as the parties mutually agree. Notification of the transfer must be given to the county's legislative delegation. If the department determines that a road in the county or municipal road system is necessary for the interconnectivity of the state highway system, and the municipality or county does not consent to the transfer, the department may initiate a condemnation action to acquire the road, or a portion of it, and the county or municipality is not required to make any further improvements to it.