Every fax has an area code.

What is an area code?

An area code is the first three digits of a ten-digit phone or fax number — the part that ties the number to a geographic region. The system is the North American Numbering Plan (NANP), which covers the United States, Canada, and much of the Caribbean. Dialing from inside North America, your carrier may add the leading country code “1” automatically, or you may need to dial it yourself, for eleven digits in all. Either way, the area code comes next — and it tells the network where your fax is headed.

Overlays: why big cities have several codes

A single area code can serve roughly eight million unique numbers. That sounds like plenty until you count every phone, fax line, and mobile device in a metro like New York, Los Angeles, or Chicago. The fix is an overlay — an additional area code assigned to the same geography. Manhattan is the classic case: 212, one of the original 86 area codes AT&T created in 1947, eventually filled up, so 917 was overlaid in 1992 (largely for mobile numbers), 646 followed in 1999, and 332 after that. A 212 number still carries a certain prestige precisely because it signals a business that has stood the test of time. Today every large U.S. city uses overlays.

Do you always have to dial the area code?

These days, almost always. There was a time when an operator connected your call and Glenn Miller could immortalize a hotel’s number as “Pennsylvania 6-5000” — no area code at all. Seven-digit local dialing survived in some communities for decades, but the 2021 nationwide rollout of the 988 lifeline pushed most remaining areas to full ten-digit dialing. When in doubt, include the area code — a fax dialed with all ten digits always routes correctly.

Your area code can move with you

Ever met someone whose cell phone still carries the area code of a city they left years ago? That’s Local Number Portability (LNP), an FCC rule that lets consumers and businesses keep their numbers when they change carriers. Wireless portability arrived in the 100 largest U.S. markets in November 2003 and everywhere else by May 2004. It applies to fax numbers, too: when you move a fax line to WestFax, your number — area code and all — comes with you.