| Start Date | 10/07/2007 |
| Current Time in Area Code 331 | 331> CDT |
| Timezone | Central Daylight Time |
| Regional Market Area | Metro Chicago |
| Population (2020) | 1581268 |
| Adjacent Area Codes | 224,464,630,708,773,779,815,847,872 |
| Overlay Area Codes | 630 |
| DuPage County |
| Kane County |
| Kendall County |
| Addison |
| Aurora |
| Bolingbrook |
| Carol Stream |
| Downers Grove |
| Elmhurst |
| Glendale Heights |
| Lombard |
| Naperville |
| Oswego |
| St. Charles |
| Wheaton |
| Woodridge |