NumberingData
Verified Nov 1, 2026 · Source: NANPA CO Code Assignment Records

BALDWIN prefixes in area code 231

NANPA records 5 assigned NXX blocks to rate center BALDWIN in area code 231, 0.9% of the 572 blocks assigned in the code. A rate center is the billing geography a block is allocated to – NANPA truncates the name to ten characters, so read it as a NANPA label rather than a town. 5 holders hold those blocks, the largest being BANDWIDTH.COM CLEC, LLC - MI (1), INTERACTIVE SERVICES NETWORK, INC. (1), 123.NET, LLC (1). The earliest assignment on record here is 2002-08-27 and the most recent 2021-05-13. 4 of them are in thousands-block pooling, so those prefixes are shared between carriers in 1,000-number lots. The same rate center name also appears in area codes 336, 337, 563, 618 – overlay codes cover the same geography, so a rate center is served by all of them.

5 assigned blocks – 0.9% of 231
5 holders of record
4 of them pooled in 1,000-number lots

Prefixes assigned here

PrefixHolder of recordAssignedPooledIn service
231-338 Bandwidth BANDWIDTH.COM CLEC, LLC - MI – yes yes
231-368 INTERACTIVE SERVICES NETWORK, INC. – no yes
231-440 123.NET, LLC 2002-08-27 yes yes
231-449 Charter CHARTER IP ENABLED SERVICES, LLC 2021-05-13 yes yes
231-745 AT&T MICHIGAN BELL TEL CO – yes yes

The holder is who received the block from the numbering administrator. It is not necessarily the carrier serving a given number: numbers move with their owners, and a pooled block is shared.

Who holds the blocks

HolderBrandBlocksShare here
BANDWIDTH.COM CLEC, LLC - MI Bandwidth 1 20%
INTERACTIVE SERVICES NETWORK, INC. – 1 20%
123.NET, LLC – 1 20%
CHARTER IP ENABLED SERVICES, LLC Charter 1 20%
MICHIGAN BELL TEL CO AT&T 1 20%

Same rate center in other codes

Overlay codes cover the same geography, so one rate center is served by all of them.

Frequently asked

Which prefixes belong to BALDWIN in area code 231?

5 blocks: 338, 368, 440, 449, 745. The table above gives the holder of each.

Which carriers have numbers in BALDWIN?

BANDWIDTH.COM CLEC, LLC - MI (1 block), INTERACTIVE SERVICES NETWORK, INC. (1 block), 123.NET, LLC (1 block), CHARTER IP ENABLED SERVICES, LLC (1 block), MICHIGAN BELL TEL CO (1 block). These are the holders on record; the carrier actually serving a given number can differ, because numbers move with their owners.

Is BALDWIN a city?

It is a rate center – the unit NANPA allocates number blocks to. Its name is abbreviated to ten characters and is not necessarily a settlement: we print it as recorded rather than guess at the full name.

Other rate centers in 231

All 572 prefixes in 231