O Fallon Missouri Area Code

One area code covers O Fallon: 636.

Scope the codes matched to O Fallon. Source geoinfo-dataset (full_dataset) ZIP→NPA (2018 snapshot) and LocalCallingGuide NPA list (2026-07 NPA list). Updated 16 July 2026. Overlay relationships come from the numbering-plan authority; the place match is computed.

O Fallon has a single code, so there is nothing to divide — every local line carries 636.

Postal geography is organised separately from telephone geography, so O Fallon’s 2 ZIP codes do not map onto the codes above. They are listed in full, with the county each falls in, on the postal side of the site.

O Fallon Missouri ZIP codes →

These are the closest places to O Fallon whose area codes are not the same set. If you are near one of them, a local number may carry a code that is not on the list above.

Straight-line distance between place reference points, not driving distance. Where a place has no Census Gazetteer point, its postal centroid is used instead.