N.J. Stat. § 27:19-1
The board of chosen freeholders may construct, or acquire by gift, purchase or condemnation, and maintain and operate, and widen when necessary, viaducts and bridges, including drawbridges, in the county, when and where the public convenience requires, and keep all viaducts and bridges wholly within the county in repair and in safe condition for public travel.
Boards of chosen freeholders of counties adjoining each other but separated in whole or in part by a ravine, marsh, river or stream, may jointly construct, or acquire by gift, purchase or condemnation, and maintain and operate, and widen when necessary, viaducts and bridges, including drawbridges, at their joint expense, over such ravine, marsh, river or stream, when and where the public convenience requires, and keep all such viaducts and bridges in repair and in safe condition for public travel.
N.J.S. § 27:19-1