Area Code 331

Area code 331 maps to 58 indexable ZIP codes on US5 across IL, with a combined ZIP-area population of about 1,440,296.

Among places with the most population in this NPA on US5 are Aurora, IL, Naperville, IL, Bolingbrook, IL, Wheaton, IL, and Downers Grove, IL. Open any ZIP below for full demographics, housing, and nearby services.

The most populous ZIP currently listed for 331 is 60505 (about 58,176 residents).

Across ZIPs with income data in area code 331, the average median household income is about $119,214 — about 59% above the U.S. median ($75,149).

Average median home value across those ZIPs is about $383,723.

On this page’s income ranking, ZIP 60521 is near the top at about $244,318.

In the North American Numbering Plan, the first three digits of a 10-digit phone number are the Numbering Plan Area (NPA), commonly called the area code. Digits 4–6 are the central office code (NXX / “exchange”), and the last four digits identify the individual line.

US5’s 331 page groups ZIP codes that are associated with this NPA in published geography data. That is a place-based view — it is not a live directory of every phone number assigned to 331, and overlays or split NPAs can mean multiple area codes serve the same metro.

Seeing area code 331 on caller ID does not prove the caller is physically in IL. Spoofing tools can display almost any NPA, including local-looking numbers used in IRS, bank, warranty, and “grandparent” scams.

If you receive an unexpected call about taxes, arrests, or locked accounts: hang up, do not share codes or remote-access software, and contact the organization using a number from its official website or your statement — not a number the caller provides. US5 publishes geography for research; it does not verify live callers.