---
title: "Area code 773: Illinois, United States"
url: "https://lookvalid.com/area-code/773.md"
canonical_url: "https://lookvalid.com/area-code/773"
last_updated: "2026-10-23"
type: "reference"
summary: "Area code 773 serves Illinois, United States. Number formats, numbering rules, a live phone validator and the other codes in Illinois."
---

# Area code 773: Illinois, United States

Area code 773 serves Illinois, United States. Number formats, numbering rules, a live phone validator and the other codes in Illinois.

NANPA lists 785 central office codes (prefixes) in use in area code 773, held by 21 holders across 11 rate centers.
Illinois Bell Tel holds the most prefixes, 257 (33%). 62% of the prefixes are pooled, which means their thousands-blocks can belong to different companies.
The FCC unwanted-call data has 3,581 complaints on file for 2,494 numbers in 773, most often filed as "Unwanted Calls". These are consumer reports, not findings.

## Facts

- In service since: 1996-10-12
- Time zone: Central (C)
- Assigned overlays: 872 (2009-11-07)
- Prefixes in use: 785
- Pooled prefixes: 484 (62%)
- Rate centers: 11
- Companies holding prefixes: 21
- Assignment dates on file: 2001-02-02 to 2025-10-15 (228 prefixes)

## Rate centers

| Rate center | Prefixes | Share |
| --- | --- | --- |
| CHICGOZN03 | 170 | 22% |
| CHICGOZN01 | 124 | 16% |
| CHICGOZN02 | 79 | 10% |
| CHICGOZN07 | 78 | 10% |
| CHICGOZN04 | 75 | 10% |
| CHICGOZN10 | 72 | 9% |
| CHICGOZN06 | 56 | 7% |
| CHICGOZN08 | 45 | 6% |
| 3 other rate centers | 86 | 11% |

## Carriers

| Holder | Prefixes | Share |
| --- | --- | --- |
| Illinois Bell Tel | 257 | 33% |
| T-Mobile USA | 169 | 22% |
| New Cingular Wireless PCS | 84 | 11% |
| Verizon Wireless | 59 | 8% |
| Mcimetro Access Transmission Services | 46 | 6% |
| Level 3 Communications | 36 | 5% |
| 15 other carriers | 134 | 17% |

A prefix holder is the company a code was assigned to, not necessarily a number's current carrier, because numbers can be ported to another company.

## History

- 1947-01-01: Area code 312, named as the parent of 773 in the NANPA report, was in service.
- 1996-10-12: Area code 773 went into service.

## Complaints on file

3,581 complaints for 2,494 numbers. Numbers whose latest complaint falls in each year:

- 2023: 120
- 2024: 137
- 2025: 102

## Questions

### Where is area code 773?

NANPA assigns area code 773 to Illinois, United States.

### In which state does area code 773 sit?

Illinois. 773 is one of 17 area codes the NANPA table assigns to the state.

### Who owns area code 773?

NANPA assigns area codes. Within 773, Illinois Bell Tel holds the most prefixes, 257 prefixes or 33%.

### Which time zone does 773 use?

The NANPA NPA report lists the time zone for 773 as Central (C).

### What year did 773 enter service?

The NANPA NPA report gives an in-service date of 1996-10-12, so 773 has been in use since 1996.

### Does area code 773 have an overlay?

Yes. 872 (in service 2009-11-07) shares the same area with 773, so numbers from all of them are local to each other.

### How many prefixes does area code 773 have?

NANPA's report dated 2026-10-17 lists 785 prefixes in service in 773, spread over 11 rate centers and 21 holders.

### Are there complaints about 773 numbers?

The FCC data on file has 3,581 complaints for 2,494 numbers in 773. They are unverified consumer reports. A number with no complaints on file is not proven safe.

Sources: NANPA central office code report dated 2026-10-17; NANPA NPA report dated 2026-10-18; FCC unwanted-call complaints, data fetched 2026-10-17; ZIP code places from GeoNames (CC BY 4.0).