Do license plate numbers mean anything? Is there any special significance or code in the number and letter comination?
It depends on the jurisdiction. In the US, each state has their own system, and, yes, sometimes they mean something such as a code indicating county of issue. Both MT and CO had such systems when I lived in them. AFAIK, my current CA plate indicates nothing. And PA was deliberately randomized, IIRC. I expect we will shortly hear details on systems in several states and countries.
Depends on the states.
As for California, I’m not sure if every combination is used but for cars at least the current format is #XXX###, and the plates are issued in order, so that if you see 4AQZ155 and 3XGE674 side by side, the “4” car was issued its license later. We rolled over from 3X to 4X in late 1997. I’m pretty sure if I got a new plate from DMV today it’d start with 4Z, though I’ve yet to see any 4Z’s on the road with my own eyes just yet, while I have seen some pretty high numbered 4Y plates. I’m sure I’m not the only one who is looking forward to seeing the California car plates roll over to 5AAA001.
Further California license trivia, they skipped over 3Y & 3Z for some reason last time.
In WV, the first number or letter on a standard license plate signifies the month the plate expires.
No, you’re not. 
Like many (most?) states, California uses different patterns for different types of vehicles. Like fiddlesticks said, cars get 1AAA111 format, while trucks get 1A11111. My pickup’s license plate, issued late in 1997, starts with 5P*****. I think they’re already in the 6’s by now.
I could be remembering incorrectly, but I think trailers here get license numbers of the form 1AA1111.
I’m not sure if this qualifies as “meaning something” or not. They’re clearly not completely random jumbles of alphanumerics here.
Now personalized plates are another kettle o’ fish entirely, but I don’t think that’s what you were asking about.
I didn’t figure it did, but I suppose you’re right that there’s a basic format which distinguishes cars from trucks, just in case you can’t tell the difference (yes, I know that it might be of marginal use when the number is recorded somewhere, and most states do have a different format for various classes of vehicles). As well as a counter within the format which allows you to see how recently the plate was issued. I don’t count that as “meaning something” either. Not like in CO where you could look at a plate and say “Oh, they’re from Weld County”. Or when I was in MT, and my “4-” prefix advertised “Missoula”.
A few bits about Massachusetts passenger plates here. All from personal observation; sorry, no cites.
White plate with green text: These started coming out around the 70s, and many are still around, because people simply have kept renewing them. And there’s only one (rear) plate; the front of your car can still look nice. Three numbers followed by three letters: ###-XXX.
White plate with red text, and “The Spirit of America” written along the bottom. These are two-plate sets, came out in the early-to-mid Nineties, and the first ones had the letters segment starting with Z, as in 123-ZCR. Later, there were Ys, and so on.
Around '97, they went to four numbers followed by two letters, and dropped the hyphen: #### XX.
Just recently, I’ve seen this the other way around; ## XXXX.
With knowlege of all this, one might be able to pass judgement as to a motorist’s age, when he/she got their plates, et cetera. When you see green text on the plate, for example, it’s almost a given that the owner has been driving for ten years at a minimum.
Also, the the last numerical digit in the plate indicates its expiration date: 123-ABC expires in March, 1234 AB expires in April, and so on. The sticker on the plate indicates the year of expiration, and the sticker is color coded. The police officer only needs to be able to read your plate and see the color of the sticker, to know if has expired.
For about a year, New Jersey had seven-letter plates with no hyphen, the format being AAA1111. Apparently people claimed this was hard to read, so they switched back to six characters in the AA-111A pattern. They blew through all of those in about six years, and then switched back to the '80s pattern of AAA-11A, starting where they left off, at JAA-11A. A few months ago they rolled over to NAA-11A after exhausting the J, K, L and M series. Interestingly, the infamous sniper’s plate was NDA-21Z, meaning he had registered the car very recently.
-Andrew L
Here’s what I can give you on the standard Hawaii plates which have the pattern of 3 letters, a space, 3 numbers.
If you see a Hawaii plate that begins with a K then that plate was issued in Kauai Co. If it begins with an M then that plate was issued in Maui Co. If it beings with an H then that plate was issued in Hawaii Co. E, F, G and J are used by Oahu Co. You may still see a D. A, B and C have since been retired when we moved from our Kamehameha plates to our rainbow plates. We don’t use I, O or Q on our plates.
Although since I’ve seen JYZ ### plates we’ve probably finished with the J’s and have probably move on to L’s. Hawaii Co. is also apparantly finished the H’s as I’ve seen HZ? ### plates. Where they’ll go I don’t know, perhaps to N.
If you see a plate with the numbers first (### T??) then that’s a commercial vehicle.
BUS plates are used by TheBus.
HPD plates are usde by the police.
C&C plates are used by the City & County of Honolulu.