Miss. Code Ann. § 65-11-31

Any county, acting through its board of supervisors, may enter into an agreement with any other county or counties, or with any road or highway district, or any other public agency for the expenditure of a part or all of the moneys available pursuant to Sections 65-11-1 through 65-11-37 for expenditure in such county or any public highway outside the boundaries of such county, if such highway is eligible for federal aid under subsection (b) of Section 3 of the Federal Aid Highway Act of 1944 [58 U. S. Stat. 838, ch. 626]. In that event, the state highway commission is authorized and empowered to expend such moneys in accordance with such agreement.