857 Area Code: Boston's Overlay on 617, Explained

857 is Boston's second area code. It doesn't have a separate territory of its own. Since 2001 it has shared the same small, dense area as the original 617: Boston, Cambridge, Somerville, Brookline and a handful of neighboring cities. An 857 number is just as "Boston" as a 617 number. It was simply issued later.

Quick reference

• Covers: the same area as 617 (Boston and its inner ring of cities)
• Started: 10-digit dialing became mandatory April 2, 2001, and 857 numbers began to be issued in May 2001
• Overlay partner: 617
• Dialing: 10 digits for every local call
• Time zone: Eastern (EST, UTC−5 / EDT, UTC−4)

The cities and towns in 617/857

The 617/857 area is small. It covers the city of Boston and the cities and towns right next to it (Wikipedia):

• Boston (including all of its neighborhoods)
• North of the Charles: Cambridge, Somerville, Everett, Chelsea, Winthrop
• West: Brookline, Newton, Watertown, Belmont
• South: Quincy, Milton

That puts the code in parts of Suffolk, Middlesex and Norfolk counties. Go a few miles further out, to places like Waltham, Lexington, Woburn, Lynn, Dedham or Weymouth, and you're in 781 and its overlay 339, which form a ring around 617 (Wikipedia). Further out are the 978/351 and 508/774 areas.

From 617 alone to 617 + 857

1947. 617 was one of the original North American area codes. At first it covered the eastern two-thirds of Massachusetts (Wikipedia).

1997. On September 1, 1997, the suburbs around Boston were split off into area code 781, which shrank 617 to roughly its current size.

Late 1990s. Demand for new numbers kept growing even after the splits. A Department of Telecommunications and Energy (DTE) commissioner said in 2001 that demand in some area codes had more than tripled in four years, driven by fax machines, pagers, cell phones and dial-up modems (Tufts Daily, April 2001).

2001. The DTE didn't split Eastern Massachusetts again. It added four overlays at once:

Ten-digit dialing became mandatory across Eastern Massachusetts on April 2, 2001, and the new codes were to be issued from May (Harvard Gazette, February 2001). So 857 wasn't the "first overlay" in the state, as is often claimed. It launched on the same schedule as 339, 351 and 774.

Why Massachusetts picked an overlay

With a split, regulators draw a new line and everyone on one side gets a new area code. With an overlay, nobody's number changes. New lines are simply assigned from the new code, but everyone has to dial 10 digits from then on.

The DTE made its reasoning plain. As a commissioner told the Tufts Daily, a split would have meant half of Eastern Massachusetts changing their phone numbers. The state had already been through two geographic splits, and people remembered how painful that was (Tufts Daily). The trade-off was ten-digit dialing, which was unpopular at first and is now routine.

Dialing 617 and 857 numbers

• Local calls: area code + seven-digit number, even 617-to-617. This has been required since April 2, 2001.
• Long distance: 1 + area code + number.
• 617 to 857 (or the reverse): a local call, dialed with 10 digits. Being in different codes doesn't make it long distance.

Since the 2001 change covered all of Eastern Massachusetts, the same 10-digit rule applies when calling 781, 339, 978, 351, 508 or 774 numbers.

857 vs. 617: what the difference tells you

Nothing about where in Boston someone is. Two neighbors on the same street can have different codes. In general, 617 numbers are older. Every 857 number was issued in 2001 or later, while a 617 number may go back much further. Locally, both read as Boston.

Is an 857 call trustworthy?

The code itself is a normal Boston code. Like any local code, 857 can be spoofed on caller ID by robocallers who want a call to look local. If an unexpected caller asks for payment, account details or a verification code, hang up and call the organization back on a number you look up yourself. Report scam calls to the FTC.

Getting an 857 or 617 number for a business

You don't need a Boston office to have a Boston number. Virtual phone providers, including Rozper, can issue an 857 number and ring it on mobiles, desk phones or a softphone anywhere. An existing 617 or 857 number can usually be ported to a new provider and kept.

Some practical points for this area:

• 617 and 857 are equivalent. If a 617 number isn't available, an 857 number covers exactly the same cities.
• Check whether your customers are really in 617/857. Customers in the suburbs see 781/339, 978/351 or 508/774 as their local codes, so a Boston number may look less local to them.
• Consider local vs. toll-free. If your customers are national rather than Boston-based, a toll-free number may suit you better. Our toll-free vs. local numbers guide and 800 area code guide cover the options.