Route 21 is a state highway in Northern New Jersey, running from the Newark Airport Interchange with US 1-9 and US 22 in Newark, Essex County to an interchange with US 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 I-78, Route 27, and I-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 I-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 US 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 description
thumb|left|Route 21 at the [[Gateway Center (Newark)|Gateway Center in Downtown Newark]]Route 21 heads north from the Newark Airport Interchange with US 1/9 in Newark near Newark Airport on a six-lane freeway known as McCarter Highway. This portion of Route 21 serves to connect Newark Liberty with downtown Newark. The route interchanges with I-78 and US 22 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 Avenue (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 and PATH's Newark–World Trade Center line. At the intersection with Emmet Street, Route 21 becomes a four-lane surface road and intersects with Murray Street, which provides access to the Ironbound neighborhood of Newark. This section of Route 21 through the southern part of Newark has a high accident rate due to the heavy concentration of businesses and traffic lights along this portion of road. The road widens to six lanes and the route intersects with Market Street (CR 510) near Newark Penn Station and continues north into Downtown Newark, splitting from the Northeast Corridor rail line. The surface portion of Route 21 in Newark, which follows the Northeast Corridor rail line, was commissioned in 1934 between Routes 25 and 29 and Market Street and the portion through downtown Newark was commissioned in 1936 between Market Street and Clay Street. Route 19 was designated in 1939 from Paterson to Belleville. In 1948, the Route 21 designation was extended north to Paterson, replacing Route 19 (which has since been reassigned elsewhere).
By Joint Resolution No. 4, approved March 22, 1934, the New Jersey Legislature designated Route 21 as the McCarter Highway, in memory of Newark financier and philanthropist Uzal Haggerty McCarter.
Freeway
Plans for a freeway along the Route 21 corridor between Newark and Paterson date back to the early 1930s and became official in 1951. In 1958, the highway was extended northward as a freeway along the west bank of the Passaic River to an interchange with Park Avenue in Nutley. Route 21 was extended to the Passaic Park interchange in 1962, Main Avenue in 1968, and Monroe Street in 1973. 1970s legislation stopped the further extension northward until environmental impact could be assessed, leaving a two-mile city street portion in place to connect to Routes 20, 46, and I-80 in Paterson for over 25 years.
thumb|left|View north along Route 21 at Exit 8 in Nutley
According to the original freeway plans, the portion north of Monroe Street was to cross over the Passaic River and terminated in Elmwood Park at the interchange of I-80 and CR 507. This routing would have allowed the highway continue with six full lanes. However, the proposal was opposed by residents who lived on the east side of the Passaic River, and for a quarter-century, traffic headed for Paterson had to use local streets in Passaic.
In the 1980s, plans were resurrected for completing the Route 21 freeway along the west bank of the Passaic River to US 46 in Clifton, avoiding the earlier objections. Official plans were made in 1996, and in late 1997, construction began on this portion of the freeway. It opened on December 20, 2000, at a cost of $136 million. However, this new route was limited mostly to four lanes (three lanes at the very northern end), utilizing the right of way of the Dundee Canal. A wider highway would have encroached on private property or the Passaic River, entailing much greater costs.
Newark section improvements
Sections of Route 21 through Newark were improved in the 1990s and the 2000s. The four-lane viaduct over the Northeast Corridor, which was built in the 1920s, was replaced between 1997 and 2003 at a cost of $253 million. A major reconstruction occurred at the interchange with I-280 at the William A. Stickel Memorial Bridge in Newark from 2015 to 2018.
On April 27, 2018, the portion of Route 21 between mileposts 3.90 and 5.83 was dedicated the "Roberto Clemente Memorial Highway" after the late baseball legend Roberto Clemente, who wore number 21 for his entire career with the Pittsburgh Pirates.