| General Information about Area Code 331 | |
|---|---|
| Country | United States |
| State / Province / Territory | Illinois |
| Major City | Lombard |
| Time Zone | Central (UTC-06:00) |
| Prefix | Primary City | County | Phone Type |
|---|---|---|---|
| 331-307 | Lombard | Dupage | Wireless |
| 331-808 | Plano | Kendall | Landline |
| 331-642 | Elmhurst | Dupage | Wireless |
| 331-216 | Oswego | Kendall | Wireless |
| 331-442 | Geneva | Kane | Wireless |
| 331-248 | Geneva | Kane | Landline |
| 331-262 | Aurora | Kane | Wireless |
| 331-803 | Homer Glen | Will | Landline |
| 331-457 | Naperville | Dupage | Wireless |
| 331-462 | Lombard | Dupage | Landline |
| 331-225 | Elmhurst | Dupage | Wireless |
| 331-980 | Aurora | Kane | Wireless |
| 331-903 | Downers Grove | Dupage | Landline |
| 331-202 | Elmhurst | Dupage | Wireless |
| 331-452 | Aurora | Kane | Wireless |
| 331-444 | Naperville | Dupage | Landline |
| 331-625 | Downers Grove | Dupage | Wireless |
| 331-814 | Naperville | Dupage | Wireless |
| 331-454 | Aurora | Kane | Wireless |
| 331-229 | Naperville | Dupage | Wireless |