Illinois Bell is AT&T's local phone company in Illinois.
Illinois Bell was the Bell phone company for most of Illinois and part of the Ameritech group. SBC bought Ameritech in 1999 and took the AT&T name in 2005, so Illinois Bell is AT&T's local phone company there today. NANPA, which runs the North American numbering plan, lists Illinois Bell as the holder of 1,909 prefixes in 2 states and territories, less than 1% of the 198,436 prefixes it has assigned.
- Name in NANPA's file
- ILLINOIS BELL TEL CO
- What it is
- AT&T's landline company
- Prefixes held
- 1,909 of 198,436 (less than 1%)
- States and territories
- 2 of 56, most in Illinois and Wisconsin
- Area codes
- 14
- Pooled prefixes
- 37%, shared in blocks of 1,000 numbers
From NANPA's central office code file of October 1, 2026. A prefix is the three digits after the area code.
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Enter the full number to see its carrier now, which may not be Illinois Bell if the number was ported. It is the same free check as our carrier lookup. To see whether it is a mobile, landline or VoIP line, use the line type lookup, and to see who it is listed to, the who called me lookup.
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A lookup shows Illinois Bell when the number is a line on AT&T's local phone network.
These are landlines and business lines that AT&T runs under the Illinois Bell name in that area, which is why the lookup does not just say AT&T.
Numbers can also move between carriers, so a lookup reads the number's carrier today, and a number with an Illinois Bell prefix can show another company if it was ported.
Illinois Bell holds the most prefixes in Illinois: 1,908 of its 1,909.
- Illinois1,908
- Wisconsin1
Illinois Bell holds prefixes in 14 area codes, and these are its largest.
A call from an Illinois Bell number is not spam just because of the carrier.
Illinois Bell lines belong to homes, offices and public services, so the carrier name says nothing about who is calling.
Caller ID can also be faked, so judge the call by what the caller asks for, never by the carrier name.
Check the full number with our free spam phone checker before you call back.
You can read about 5 more carrier names here.
These are the questions people ask about Illinois Bell.
What is Illinois Bell?
Illinois Bell was the Bell phone company for most of Illinois and part of the Ameritech group. SBC bought Ameritech in 1999 and took the AT&T name in 2005, so Illinois Bell is AT&T's local phone company there today.
Why does a phone lookup say Illinois Bell?
A lookup shows Illinois Bell when the number is a line on AT&T's local phone network. These are landlines and business lines that AT&T runs under the Illinois Bell name in that area, which is why the lookup does not just say AT&T. Numbers can also move between carriers, so a lookup reads the number's carrier today, and a number with an Illinois Bell prefix can show another company if it was ported.
Is a call from an Illinois Bell number spam?
Illinois Bell lines belong to homes, offices and public services, so the carrier name says nothing about who is calling. Caller ID can also be faked, so judge the call by what the caller asks for, never by the carrier name. Check the full number with our free spam phone checker before you call back.
How many phone prefixes does Illinois Bell hold?
NANPA lists Illinois Bell as the holder of 1,909 prefixes, less than 1% of all assigned US prefixes. A prefix is the three digits after the area code and covers up to 10,000 numbers. 37% of these are pooled, so blocks of 1,000 numbers inside them can belong to other carriers.
Which states have the most Illinois Bell prefixes?
Illinois (1,908) and Wisconsin (1) have the most, out of 2 states and territories.
Can I find out who owns an Illinois Bell number?
Illinois Bell does not publish who uses its numbers. Our free who called me lookup shows who a US number is listed to and the city and state on the listing, when the number has a listing.
Source: NANPA, the North American Numbering Plan Administrator: its central office code assignments, as of October 1, 2026. Company histories are from public records and each company's own descriptions.