Miss. Code § 65-11-11
The amount of federal funds made available to the State of Mississippi for secondary and feeder roads under the Federal Aid Highway Act of 1944 [58 U. S. Stat. 838, ch. 626] which is allotted to the counties as provided in Section 65-11-9, shall be apportioned among the counties of this state by the State Highway Commission in the following manner: one third in the ratio which the area of each county bears to the total area of the state; one third in the ratio which the rural population of each county bears to the total rural population of the state, as shown by the federal census of 1940; and one third in the ratio which the mileage of rural delivery and star routes in each county bears to the total mileage of rural delivery and star routes in the state. The amount of federal funds so apportioned to each county shall be matched by state funds apportioned to the State Highway Fund to carry out the purposes of Sections 65-11-1 through 65-11-37 as hereinafter provided; in the event the amount so appropriated for such State Highway Fund is insufficient to entirely match the federal funds allotted to county highways, then the amount of such fund shall be apportioned among the counties in the same manner as herein provided. "Rural population" and "rural delivery" routes as used in this section shall have the same meaning ascribed to them in the Federal Aid Highway Act of 1944 [58 U. S. Stat. 838, ch. 626].
Miss. Code § 65-11-11