Miss. Code § 65-11-7
There is hereby created a system of county federal aid highways, for the purposes of Sections 65-11-1 through 65-11-37, and the county highways which shall comprise and constitute such system shall be selected jointly by the boards of supervisors of the various counties and the State Highway Commission of Mississippi, as same may be supplemented from time to time. Projects for the construction and improvement of such county highways shall likewise be selected jointly by the several boards of supervisors and the State Highway Commission, provided however, that in all cases where such system and projects thereon have been heretofore selected and agreed upon by the several boards of supervisors and the State Highway Commission as required by the Federal Aid Highway Act of 1944 [58 U. S. Stat. 838, ch. 626], the highways thereby selected shall constitute the roads in the affected counties which shall be a part of the county federal aid highway system, and such selections and agreements are hereby ratified and approved.
Miss. Code § 65-11-7