Question 1

Why does my city have more than one area code?

Accepted Answer

Because it ran out of available phone numbers in the original code. Rather than change everyone's number (a 'split'), the phone system now usually adds an 'overlay' — a second area code covering the exact same region — so new numbers can keep being assigned. That's why one metro can be served by three or four area codes.

Question 2

What's the difference between an overlay and a split?

Accepted Answer

A split divides a region into pieces and gives one piece a brand-new area code, so people in that piece have to change their number. An overlay lays a new area code over the same region without changing any existing numbers — the trade-off is that everyone must dial all 10 digits. Modern capacity relief is almost always done with overlays.

Question 3

Why do I have to dial 10 digits now?

Accepted Answer

Because your area has an overlay. When two area codes cover the same region, the phone network can't tell which one you mean from 7 digits alone, so 10-digit dialing (area code + number) becomes mandatory for everyone in the overlay — even for local calls.

Question 4

Does an overlay change my phone number?

Accepted Answer

No. Existing numbers keep their original area code. Only newly assigned numbers get the new overlay code. (A split, the older method, did force number changes — which is part of why overlays replaced it.)

Overlays and splits: why your city has more than one area code

Split vs overlay

Why you now dial 10 digits