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Yes, I know that is the current way they work (...and I said it in my comment?)

My point is that postal codes aren't "supposed" to work any particular way. They work in what ever way they are specified to work at any particular point in time in any particular place.

Zip codes in the US are related to delivery routes. Prior postal codes in the US were not. UK post codes are currently hyperspecific to a single location. Previously they were not.

by russdill16 hours ago|

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In the US they were always tied to routes. The first number gives a set of distribution centers, and the second two numbers where specifically to go. If you look at a map of the first number, you'll see sharp lines separating the states. It'd be hard to verify historically, but if you look at zip codes near the border for, say, 89439, several addresses on the California side use the 89439 zip code.

It'd find it difficult to believe that when the system was originally created, mail delivered by a Nevada post office to a physical location in California had a zip code starting with a 9 rather than an 8.

by kube-system16 hours ago|

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Zip codes aren't even quite specific enough to get to the route level. But postal codes in the US pre 1962 were not even zip codes.

My grandfather's postal code growing up in the US was simply "6". He did not have a zip code, because they had not been invented yet.

We didn't quite get enough info to determine the particular route until Zip+4 in 1983.

> It'd find it difficult to believe that when the system was originally created, mail delivered by a Nevada post office to a physical location in California had a zip code starting with a 9 rather than an 8.

When the US first implemented postal codes, 100+ cities had a duplicate postal code of "1", which was the first postal zone within that particular city. We've increased the specificity of our postal codes twice since then. (well, three times if you count IMb)

But more to your modern zip code example -- addresses and their 5 digit ZIP codes historically followed the post office together in lock step. (This is why many system have separate "mailing addresses" from "physical addresses", they weren't always the same thing) -- e.g. if you lived in rural town and your mail was delivered from a different town you'd have something like a rural route address and both the municipality and the zip code you'd put on the letter would be for town the post office was in, not the town you lived in.

For example, when I was young and wrote a letter to my grandmother, I wouldn't put her street address on it... because she didn't have one. I'd address it to her rural route number and box number, and I would address it not to the town she lived in, but to the town the post office was in, and the zip code of that post office.

In the case where this was across state lines, your mailing address would be a different state than where you lived.

This is part of the reason why USPS has been converting from RR addresses to the Locatable Address Conversion System. Because it was difficult for first-responders to find homes when people calling didn't have addresses that matched where they actually were.