Tennessee Code Title 5. Counties § 5-2-101

(a) New counties may be established by the general assembly that consist of not less than two hundred seventy-five square miles (275 sq. mi.), and that shall contain a population of not less than seven hundred (700) qualified voters.

(b) No line of such county shall approach the courthouse of any old county from which it may be taken nearer than eleven (11) miles, nor shall such old county be reduced to less than five hundred square miles(500 sq. mi.).

(c) No part of a county shall be taken off to form a new county or a part thereof without the consent of two thirds ( 2/3 ) of the qualified voters in such part taken off; and where an old county is reduced for the purpose of forming a new one, the seat of justice in the old county shall not be removed without the concurrence of two thirds ( 2/3 ) of both branches of the general assembly.