New Jersey Route 3 in the context of "U.S. Routes 1 and 9"

U.S. Route 1/9 (US 1/9 or US 1-9) is the 31.0-mile-long (49.9 km) concurrency of US 1 and US 9 from their junction in Woodbridge in Middlesex County, New Jersey, north to New York City. The route is a multilane road with some freeway portions that runs through urbanized areas of North Jersey adjacent to New York City. Throughout most of its length in New Jersey, the road runs near the New Jersey Turnpike (Interstate 95 [I-95]). In Fort Lee, US 1/9 merges onto I-95 and crosses the Hudson River on the George Washington Bridge, where the two U.S. Routes split a short distance into New York. US 1/9 intersects several major roads, including I-278 in Linden, Route 81 in Elizabeth, I-78 and US 22 in Newark, Route 139 in Jersey City, Route 3 and Route 495 in North Bergen, and US 46 in Palisades Park. US 1/9 also serves as the primary access point to Newark Airport. Between Newark and Jersey City, US 1/9 runs along the Pulaski Skyway. Trucks are banned from this section of road and must use Truck US 1/9. The concurrency between US 1 and US 9 is commonly referred to as "1 and 9". Some signage for the concurrency, as well as the truck route, combines the two roads into one shield, separated by a hyphen (1-9) or an ampersand (1&9).

The current alignment of US 1/9 south of Elizabeth was planned as Route 1 in 1916; this road was extended to the Holland Tunnel in Jersey City in 1922. When the U.S. Highway System was created in 1926, US 1 and US 9 were marked concurrent through northern New Jersey between Rahway on the current alignments of Route 27 and Truck US 1/9. In 1927, Route 1 became Route 25, and Route 1 and Route 6 were legislated along the current US 1/9 north of Jersey City. US 1/9 originally went to the Holland Tunnel on Route 25; after the George Washington Bridge opened, the two routes were realigned to their current routing north of Jersey City. After the Pulaski Skyway opened in 1932, US 1/9 and Route 25 were routed to use this road, which soon had a truck ban resulting in the creation of Route 25T (now US 1/9 Truck). South of Newark, US 1/9 was moved from Route 27 to Route 25. In 1953, the state highways running concurrent with US 1/9 in New Jersey were removed. In 1964, the approaches to the George Washington Bridge were upgraded into I-95.

Route 21 is a state highway in Northern New Jersey, running 14.35 mi (23.09 km) 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.