N.J. Stat. Ann. § 40:9A-1

Any county or counties, municipality or municipalities, or any combination thereof, operating libraries pursuant to chapters 33 or 54 of Title 40 of the Revised Statutes may, by contract or agreement, by and between the appropriate board or boards of chosen freeholders and the municipality or municipalities, establish and maintain a federation of their libraries for the purpose of providing such co-operative library services as shall be thereby agreed upon.