Tennessee Code Title 49. Education § 49-50-105

(a) For participation in the benefits of this part, contiguous counties may cooperate and be regarded as one (1) county in the employment of either a county agricultural agent or county home demonstration agent, or both; provided, that the combined area of the counties cooperating does not exceed eight hundred square miles (800 sq. mi.) and that the assessed valuation of one (1) of the counties does not exceed five million dollars ($5,000,000).

(b) The plans for such cooperation shall be arranged by the county mayors of the respective counties involved, and approved by the director of extension work of the University of Tennessee.