Clifton is a city in Passaic County, in the U.S. state of New Jersey. Criss-crossed by several major highways, the city is a regional commercial hub for North Jersey and is a bedroom suburb of New York City in the New York Metropolitan Area. As of the 2020 United States Census, the city retained its position as the state's 11th-most-populous municipality, just behind 2020 #10 Trenton, and well ahead of 2020 #12 Cherry Hill, with a population of 90,296, reflecting an overall increase of 6,160 (+7.3%) from the 2010 census count of 84,136, which in turn reflected an overall increase of 5,464 (+6.9%) from the 78,672 counted in the 2000 census. The Census Bureau's Population Estimates Program calculated that the city's population was 88,709 in 2022, reflecting an overall decrease of 1,587 (1.8%) from the 90,296 counted in the 2020 census and ranking the city the 388th-most-populous in the country.

Route 21 is a state highway in northern New Jersey, running 14.35 mi (23.09 km) from the Newark Airport Interchange with U.S. Route 1/9 (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 Interstate 78 (I-78), Route 27, and I-280 in Newark, Route 7 in Belleville, and Route 3 in Clifton.