Williamson County ZIP Codes

Williamson County is a county of Illinois.

ZIP codes: 11
Cities & towns: 11
Area codes: 2
Land area: 420 sq mi

Every ZIP code in Williamson County

628xx–629xx

The complete list of Williamson County, IL ZIP codes with the city each one delivers to.
ZIP code	City
62841	Freeman Spur
62915	Cambria
62918	Carterville
62921	Colp
62922	Creal Springs
62933	Energy
62948	Herrin
62949	Hurst
62951	Johnston City
62959	Marion
62974	Pittsburg

We do not publish a delivery type (standard, PO box, unique) or a neighbourhood for each ZIP. USPS delivery-type products are licensed, and no clean-rights source maps ZIP codes to neighbourhoods — so the Williamson County codes above are listed without a column we would have to invent.

Cities and towns in Williamson County

Area codes covering Williamson County

Telephone and postal boundaries are drawn by different bodies, so these codes overlap the county without matching its edges.

Where Williamson County's ZIP codes sit

Each point is the reference point of one Williamson County ZIP code, plotted from its record coordinates. The outline is the convex envelope of those points — a footprint, not a boundary.

Reference points and footprint
Not an official NANPA boundary
Not a USPS delivery area

Scope every ZIP code recorded in Williamson County. Source GeoNames US postal codes (2026-07 postal dump), Census 2024 county Gazetteer (2024 Gazetteer) and geoinfo-dataset (full_dataset) ZIP→NPA (2018 snapshot). Updated 16 July 2026. The outline is a convex envelope of ZIP reference points, not a jurisdiction boundary.