(a) The portion of State Highway 21 in Nacogdoches County between County Road 713 and County Road 782 is designated as the Sergeant Tom Sitton Memorial Highway.
(b) Subject to Section 225.021(c), the department shall:
(1) design and construct markers indicating the designation as the Sergeant Tom Sitton Memorial Highway and any other appropriate information; and
(2) erect a marker at each end of the highway and at appropriate intermediate sites along the highway.