N.J. Stat. Ann. § 19:8-5

An American flag, approximately 3 feet by 5 feet in size, shall be displayed at the outside entrance of each polling place in this State by the district boards during the hours when the boards are in session; except that, when more than one polling place is located in the same building the prominent display of one such flag at the outside entrance used in common to reach more than one polling place shall constitute compliance with the provisions of this section. Such flag shall be furnished by the clerk of the county and delivered to the municipal clerks for distribution.