S.C. Code Ann. § 57-5-1470

All turnpike bonds issued under this article, and the interest thereon, are exempt from all state, county, municipal, school district, and other taxes or assessment, direct or indirect, general or special, imposed by the State of South Carolina, whether imposed for the purpose of general revenue or otherwise, except inheritance, estate, or transfer taxes. Each turnpike facility constitutes a portion of the state highway system and as such is not subject to ad valorem or other forms of taxation by the State or any of its political subdivisions.