New Jersey Route 21  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 Newark 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. Route 21 was created in 1927 to run from Newark to Belleville. In 1948, the route was extended north to Paterson. In the 1950s construction began on the freeway portion of Route 21 and it was completed in stages between Chester Avenue in Newark and Monroe Street in Passaic between 1958 and 1973. Plans were made to extend the freeway north to Interstate 80 in Elmwood Park; however, they were opposed by residents living on the east side of the Passaic River. In the 1980s, another northern extension of the Route 21 freeway was proposed to U.S. Route 46 in Clifton; this section was built between 1997 and 2000. The surface portion of Route 21 through Newark underwent many improvements in the 1990s and 2000s. Route 21 heads north from the Newark Airport Interchange with U.S. Route 1/9 and U.S. Route 22 in Newark near the Newark Liberty International Airport on the six-lane, divided McCarter Highway. This portion of Route 21 serves to connect Newark Liberty with downtown Newark. The route interchanges with Interstate 78 and then crosses over Conrail Shared Assets Operations' Greenville Running Track, Lehigh Line, and Passaic and Harsimus Line and then Amtrak's Northeast Corridor rail line on a viaduct, coming to an interchange with Broad Street that provides access to Frelinghuysen Ave./Route 27. The route continues north, paralleling the elevated Northeast Corridor tracks that lead up to Newark Penn Station, which serves Amtrak and NJ Transit trains.