Route 21 is a highway in northern New Jersey, running from the Newark Airport Interchange with U.S. Route 1/9 and U.S. Route 22 in Newark, Essex County to an interchange with U.S. Route 46 in Clifton, Passaic County. The route is a four- to six-lane divided highway known as McCarter Highway on its southern portion in Newark that serves as a connector between the Newark and Paterson areas, following the west bank of the Passaic River for much of its length. It also serves as the main north–south highway through the central part of Newark, connecting attractions in downtown Newark with the Newark Liberty International Airport. The portion of Route 21 through Newark is a surface arterial that runs alongside the elevated Northeast Corridor rail line through the southern part of the city and continues north through Downtown Newark while the portion north of Downtown Newark is a freeway. Route 21 intersects many major roads including Interstate 78, Route 27, and Interstate 280 in Newark, Route 7 in Belleville, and Route 3 in Clifton.