Area Code 557 — Florissant, Missouri

NANP area code

557

UTC−6, UTC−5 during daylight saving

State
Missouri
Primary city
Florissant
Time zone
Central
In service
2022
Overlay
314

The code reaches 33 communities and 7 counties and independent cities across Missouri.

Was this call legitimate?

The area code itself carries no risk signal. 557 is assigned to Florissant, Missouri, so a call from it is consistent with a real caller in that area — but the digits alone prove nothing, because they can be forged.

Caller ID is set by whoever places the call, not verified by the network. That is why neighbour spoofing works: an operation anywhere in the world can display a number that matches the area code — and often the first three digits after it — of the person being called, so the call looks local. Every community in the 557 territory is a plausible-looking origin for a forged 557 number, which is why one can be made to look like a neighbour to so many people. The same applies to its overlay code 314, which serves the same ground.

If you did not recognise the call: let it go to voicemail — a legitimate caller with real business will leave one. Do not return the call using the number shown; look the organisation up independently and call the number you found. Never confirm personal details, card numbers, or one-time codes to someone who called you, however plausible the number looked.

Codes.zone publishes no complaint counts, risk scores, or caller identities. We hold no data on individual numbers and will not estimate what we cannot source.

Local time and when to call back

Time there now

Central · UTC−6, UTC−5 during daylight saving

Reasonable callback window

8:00 AM – 9:00 PM

local time in Central

Federal rules bar telemarketing calls to a residence outside 8:00 AM–9:00 PM in the called party's own time zone. It is a sensible bound for a personal callback too — and a caller who rang you well outside it was not observing it.

Overlay codes and ten-digit dialling

557 does not have its territory to itself. 314 covers the same ground, serving Florissant and the rest of the 557 territory. An overlay is what a regulator adds when a region runs out of assignable numbers: rather than splitting the area and forcing half the residents to change their number, a second code is laid over the top and new numbers are issued from it.

The practical consequence: two neighbours on the same street can hold numbers in different area codes, so the code tells you nothing about which part of town a caller is in — and local calls must be dialled as all ten digits, because seven is no longer unambiguous.

Cities served

largest 20 by ZIP count
Communities served by area code 557, ranked by how many ZIP codes each holds.
CityZIP codesCounty or independent city
Saint Louis68St. Louis city
Ballwin4St. Louis County
Florissant4St. Louis County
Saint Charles4St. Charles County
Chesterfield3St. Louis County
Rolla3Phelps County
Fenton2St. Louis County
Arnold1Jefferson County
Barnhart1Jefferson County
Bridgeton1St. Louis County
Cottleville1St. Charles County
Earth City1St. Louis County
Eureka1St. Louis County
Flinthill1St. Charles County
Gray Summit1Franklin County
Grover1St. Louis County
Hazelwood1St. Louis County
High Ridge1Jefferson County
Imperial1Jefferson County
Kewanee1New Madrid County

13 further communities not listed. All Missouri area codes →

Each point is a community served by 557, plotted from its record coordinates. The outline is the convex envelope of those points — a footprint, not a boundary.
  • Reference points and footprint
  • Not an official NANPA boundary
  • Not a USPS delivery area

Scope every community matched to 557. Source geoinfo-dataset (full_dataset) ZIP→NPA (2018 snapshot), GeoNames US postal codes (2026-07 postal dump) and Census 2024 county Gazetteer (2024 Gazetteer). Updated . Coordinates are place reference points, not boundaries.

Counties and independent cities

Prefixes inside 557

We do not publish the NXX prefixes inside 557. The assignment of prefixes to rate centres comes from LERG routing data, which is proprietary, and we will not estimate it from postal data — ZIP codes and telephone prefixes do not map onto each other. Awaiting a clean-rights NPA-NXX source.

Why this code exists

557 is the newer code here, added in 2022 over 314 (1947). The older code had run out of exchanges to assign, and an overlay avoids the alternative — splitting the region and forcing half its residents to renumber. New lines have been issued from 557 since.