N.J. Stat. § 30:8-20
In any county where the board of chosen freeholders shall assume the custody, rule, keeping and charge of the county jail and of the prisoners therein, as provided by section 30:8-19 of this Title, such board shall, by the votes of a majority of all its members for the time being, appoint some fit person to be the keeper or warden of the jail or jails of the county, who shall hold his office for the term of five years and until his successor shall be appointed in his stead and shall have duly qualified and given bond. Such keeper or warden may be removed from office at any time, by the affirmative votes of two-thirds of all the members of the board of chosen freeholders of the county for the time being, for good cause appearing to them. Such keeper or warden before he enters upon the discharge of the duties of his office shall give bond to such board of chosen freeholders, in such sum and with such sureties as such board shall prescribe, conditioned for the full and faithful performance of the duties of his office; provided, however, that where any county has adopted the provisions of Title 11 of the Revised Statutes (Civil Service) and the warden or keeper of the county jail has held his said office by virtue of the provisions of said Title 11 of the Revised Statutes, upon such transfer of the custody of the jail to the board of chosen freeholders, such warden in office at the time of the passage of this act, shall continue to hold his said office and enjoy tenure therein subject to all of the provisions of said Title 11 of the Revised Statutes.
N.J.S. § 30:8-20