N.J. Stat. § 40:20-2
Boards of chosen freeholders in counties of the first class governed by sections 40:20-2 to 40:20-19 of this title shall consist of nine members.
They shall be elected by the voters of the county at the general election and shall hold office for three years from the annual stated meeting of the board next after their election and until their successors are elected and qualified.
The first election under this section shall be held at the general election next preceding the expiration of the terms of office of the members of the board in office at the time when said sections 40:20-2 to 40:20-19 take effect in any county.
At the first election in counties where the terms of office of all the members of the board expire at the same time, there shall be elected three members for one year, three members for two years and three members for three years, and the ballots shall designate which members are to serve for the terms of one, two and three years respectively.
At the first election in counties where the terms of office of the members of the board expire at different times, there shall be elected three members for three years, and at succeeding elections there shall be elected three members for the term of three years.
The members so elected from time to time, together with the members of the board whose terms shall not have expired, shall constitute the board of chosen freeholders until all the members thereof are elected under this section.
N.J.S. § 40:20-2