Your ZIP code is a piece of postal logistics. It tells a mail carrier which post office handles your block. The system was introduced on July 1, 1963 to sort envelopes faster, not to say anything about history or neighborhood or who belongs where. But in Montclair, the line between 07042 and 07043 traces a boundary that is nearly 330 years old and understanding what was already here when the numbers arrived is the whole story.
The two settlements
Cranetown and Speertown were separate communities with separate origins, divided by Watchung Avenue. The English settlers in the south and the Dutch settlers in the north farmed different land, spoke different languages and had no particular reason to think of themselves as one place.
John Speer, a Dutch settler whose home still stands on Upper Mountain Avenue just north of today’s Montclair border, gave the northern community its name. The Crane family gave the south its name and its commercial energy. By the early 1800s, Cranetown had grown into a small commercial hub. Speertown remained a rural hamlet.
The railroad and what followed
The arrival of the Newark and Bloomfield Railroad in 1856 changed both halves of town. New residents followed the tracks, businessmen, their families, and the immigrant and Black families drawn by work and opportunity. Between 1880 and 1930, more than 37,000 people moved to Montclair.
“I would say the 07042 of Montclair, you start to see a lot more immigrant and Black families moving in, living, co-together in different communities historically,” Angelica Diggs, director of the Montclair History Center, told Montclair Pod hosts Farnoosh Torabi and Mike Schreiber during a recent visit. “The 07043 of Montclair ended up keeping itself a little bit more separated.”
Redlining
In the 1930s and ’40s, federal housing agencies graded residential neighborhoods by mortgage risk, and local banks enforced those grades. The practice, redlining, concentrated Black and immigrant families in specific areas and restricted others by design. What had been an informal north-south divide became official government policy, written into the maps that determined who could build equity and who couldn’t. By the time the postwar boom arrived, the divide was structural.
1963: When the ZIP codes arrived — and what they found
On July 1, 1963, the U.S. Post Office introduced the Zone Improvement Plan (ZIP) nationwide. The country was processing 63 billion pieces of mail a year, and the old system routed each letter through an average of 17 sorting stops. ZIP codes were the fix: a five-digit number assigned to each post office or delivery station that allowed mail to be sorted by machine.
The codes were not drawn to reflect neighborhoods. They were not drawn to reflect demographics, school districts or property values. They were drawn around post offices, specifically, around whichever post office delivered to your block.
Montclair had two post offices. One served the town center and the other served Upper Montclair. When July 1, 1963 arrived, those two offices became 07042 and 07043.
Ultimately this new postal delineation followed, almost exactly, the old line between Cranetown and Speertown, the same Watchung Avenue boundary that had separated an English settlement from a Dutch one in the 1690s, that had informally sorted immigrant and Black families from wealthier white ones in the early 20th century, and that federal housing policy had formalized in the 1930s.
What the numbers still carry
A five-digit code designed to move envelopes faster ended up shaping how Montclair neighborhoods were priced, funded and perceived for decades. The differences between 07042 and 07043 did not start with the postal system. But the postal system gave those differences a name that stuck and that name is still on every piece of mail you receive.
If you want to see how your specific block was graded during the redlining era, the University of Richmond’s Mapping Inequality project is free and searchable by address. And if the history of your ZIP code has you curious about your own block’s deeper story, we have a story on the Montclair History Center to get started.
Montclair’s history
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