N.J. Stat. § 30:8-12
In county penitentiaries and county jails in counties of the first class in this state the female prisoners shall be, as far as the construction of the jail or penitentiary will permit, removed from the quarters occupied by the male prisoners; and the board of chosen freeholders, in the case of such county penitentiary, and of the sheriff of the county, in the case of such county jail, shall appoint one or more female guard or guards over such female prisoners at all hours during the night, the salary of such female guard or guards to be fixed and paid in the same manner as the salaries of the male guards are fixed and paid. No woman appointed to be such guard shall be under the age of twenty-five years or over the age of forty years when so appointed.
N.J.S. § 30:8-12