But, if there's an address already, what's the point of the postcode, exactly?

Isn't this just, like, the address again?

Kind of, yes, but also no, because there's two answers to why this, if also that.

For the first, while every country has their own postcode particulars, to start simple, we're going to start with the states, who stick with just simple digits.

But, does it a bit different by being the only one on Earth to call their code a zip code, along with the Philippines?

But, anyway, the usual way to describe how this five-digit code works is by starting with the first digit to divide America into ten zones.

Beginning with New England as zero, and, oh, New Jersey, too?

Really, America?

There's a non-contiguous exception before we've even counted to one?

So, New England-ish, I guess?

Oh, but also Puerto Rico?

And the Virgin Islands, only 7% of the Earth's circumference away?

Well, that's quite the group to group together.

We'll call it Greater Atlantia, I guess.

Moving on to number one, this contains the Keystone Empire, plus Delaware.

Two spans the North-South, three covers the Deep South, four stretches the Old Northwest, five reaches the Highland, six centers the Heartland, seven connects the Crossroads, eight rises the Mounted West, and nine claims everything else.

The West Coast, of course, and Alaska and Hawaii, as usual.

But also, don't forget American Samoa, Guam, and the CMNI, which make Greater Pacifica to Nearer Atlantia.

So these are the ten regions told by the first digit of the zip code.

Digit two divides again, as in the Highlands, five.

Five-nine for Montana, five-eight for Dakota, and seven for South.

Though, with Minnesota, missed much more populous, digit two splits the state in twain.

In Iowa, even more.

Five-oh, five-one, five-two.

Now, you can make a map of America's zip digits one and two that looks like this.

But it's not quite right, for the actual area the codes cover looks more like this, with lots of holes.

And, yes, that's a lot of overlap with the federal land map for the same reason.

No one lives here.

Parks, forests, deserts, no deliveries, no codes needed.

Yes, yes, you got there.

This means zip codes are doing something very different from, say, GPS codes, which can point to any place on Earth exactly.

Which is the clue that there's something strange about this map and the real way zip codes work.

But let's play pretend again and color the map back in.

Still, closer inspections shows, with the double digits, the map is all melty and pointy, with cross-border exceptions everywhere.

So what's happening here?

Well, digit three reveals an even stranger map, with wild blobs of land that don't make any sense at all, because we've been trying to do this all wrong.

These three digits don't mark out land.

These digits mark out infrastructure.

The zip code first three digits point to a specific big building, a sectional facility center, a belted behemoth bundling up all the mail it ingests for who?

Not you, but to ship to all the post offices within its area of influence.

So that's why this map is all melty, because the map isn't really real.

Rather, there are sorting centers scattered strategically, each numbered, and each sorts the mail for the post offices it can reach efficiently.

So, if you live on the edge of your state, but near another state's sorting center, your zip code follows the sorting code, not the state line.

So, much simplified, here's what happens when you mail a letter.

Digit the first sends it to a zone sorting center, which, when it arrives, is then sorted by digits the second and third to be sent to the sectional sorter, which, when it arrives there, is then again sorted by digits the fourth and the fifth to the local post office.

And this is where Americans are vaguely aware they're supposed to include four more digits at the end of a zip code, but no one does, because America tried to bolt on the plus-four code long after her citizens had already learned that the first five alone would get the job done, and so didn't bother, with only the most postal perfectionists plus-fouring their packages.

But, as a reward, they do get sorted and sent faster, because the final code is for the final sort at the final post office, onto final truck for the final delivery.

And so, the greater geographical oddities of the zip code are less odd, because the zones aren't zones, they're the first step in sorting.

A giant fork in the road.

Greater Atlantia this way, everything else that way.

Then down the road, islands to the left, New England to the right.

So the first answer to why this, if also this, is because the address is where to go, but the post code is how to get there.

The journey, not the destination.

And most countries' codes are built the same basic way.

Simple, human-readable directions left to right, more characters reveal more directions to get the letter closer to where it's going, and the address only needed after it's sorted into the truck and the destination within sight.

UK probably has the best version of this, adding letters to make sorting centers more memorable.

Manchester gets all the M's, Oxford the O's, yo, York, lovely London, as capital, gets all the compass points.

But the rest, simplified, is the same story.

The next digit sorts to a post office, and the last to a delivery route.

And because the UK code uses letters, and is longer than America's, UK codes can sort close enough to almost replace the address entirely.

In most cases, you could get away with just the code and the house number and still expect delivery.

I mean, I don't live that dangerously, but I'm also the kind of person who writes plus four on my American Mail.

But looking at this, it's kind of silly me, right?

If an old post code can get this close on its own to replacing the address, if someone started over now, could it be done better?

And that's exactly what Ireland thought.

Hey guys, you know we've got GPS codes now, right?

People don't want to write a long code like that.

Yeah, yeah.

But also, this system was written for human sorters centuries ago.

We've got giant sortatrons now.

Who cares?

We don't really need that.

Wait, what are you doing?

I think I'm going to start over.

How?

I'm going to go random.

Which you did, dividing up the country intentionally, unmemorably.

Cork, your codes start with T12.

Limerick, V94.

Waterford, X35.

That's horrifying, but I guess America's first digit is basically meaningless as well.

But Ireland didn't stop there and went random all the way down, running like mad past every single point in the whole country where mail might be delivered to slap four more characters at complete random on the door.

And it matters not at all, because Ireland created the codes for the giant sortatrons, who can read them and compare them to the big list of all codes in the country, where the last four, surprise, are a GPS code in disguise.

Which pinpoints the exact place the letter's supposed to land.

And since the sortatrons also know where all the mail trucks go, it's easy-peasy for the sorters to sort, while still being not too hard for the little humans to remember the little bitty codes to write on their pieces of paper to pass their notes back and forth.

And the random postcodes has one more bonus.

In other countries, when towns grow or ghost, buildings divide or combine, countries that try to keep their codes in order-ish have to move the codes around to maintain that order-ish.

And the poor humans with houses that haven't changed having to remember now that their new code is just a little different.

But not in Ireland, for there's no order to maintain at all.

If your mailbox never moves, your code never changes.

That's the method to the madness.

So, when Ireland asks herself why this, if also this, she found a new answer.

Make a postcode so precise it becomes the perfect address.

So while everywhere else you have to write both the destination and the journey, in Ireland you can write both, probably still should write both, but you don't have to because just the postcode alone will do.

This all looks quite complicated.

Did you guys consider ever using just one postcode for your country?