(1) There is hereby created a civil service commission to administer a civil service system in every municipality described in subsection (2) of this section which has administrative and other employees employed on a monthly basis.
(2) The provisions of subsection (1) of this section shall apply to: Any municipality, operating under a commission form of government, and having a population of more than twenty-one thousand, according to the federal census of 1950; and
(3) Any municipality located in the Yazoo-Mississippi Delta Levee District, and having a population of more than fifteen thousand and less than twenty thousand, according to the federal census of 1950.