N.J. Stat. § 44:1-38

The boards of chosen freeholders respectively in any two or more contiguous and adjoining counties may resolve that: a. Upon a like resolution being adopted in such other adjoining and contiguous county or counties as are named therein; and b. Upon the ratification and acceptance as provided in this chapter by a majority vote of the legal voters in such counties of the provisions of such resolutions of like purport as have been adopted in the respective counties, excepting from the vote the electors of municipalities which maintain their own permanent poor in institutions and have, as authorized in section 44:1-61 of this title, elected not to participate in such purpose-- provision be made for the permanent relief of the poor in such counties in a welfare-house to be jointly owned by such counties, or so many thereof as adopt the plan, or as the resolutions may provide, which shall constitute a district and be conducted by a welfare board constituted as provided in section 44:1-43 of this title, for the permanent relief of the poor of such counties. In such case permanent relief shall be provided for the poor of such counties, except those municipalities which maintain their own permanent poor and which have elected not to participate for such purpose in the jointly maintained district welfare-house.