 In 1948, the Route 21 designation was extended north to Paterson, replacing Route 19 (which has since been reassigned elsewhere).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.