636 Area Code — O'Fallon, MO
Area code 636 serves O'Fallon and 3 other cities in Missouri. Local time follows America/Chicago. It has no overlay codes.
- State
- Missouri
- Primary city
- O'Fallon
- Timezone
- America/Chicago
- In service since
- 1999
- Type
- Geographic
- Overlay codes
- None
Cities Served by 636
The 636 area code covers 4 cities and communities in Missouri.
- O'Fallon
- Saint Charles
- Wentzville
- Chesterfield
About Area Code 636
Area code 636 is a North American Numbering Plan (NANP) area code that has been in service since 1999. It is administered by NANPA on behalf of the FCC and serves the Missouri region anchored on O'Fallon.
636 is currently a single-coverage geographic area code with no overlays. This means a 7-digit number in this area code is unique within its rate centers, though best-practice is always to dial the full 10-digit number when contacting a 636 line.
Mobile numbers in 636 are portable: a person who moved away from O'Fallon may still carry a 636 mobile number on their device. If you receive an unexpected call from a 636 number, run it through the reverse lookup tool above for the most accurate, free identification.
If you live or do business in Missouri, you may also interact with neighbouring or overlay codes. See the related codes section below to explore the rest of Missouri.
Other Missouri Area Codes
Continue exploring the Missouri numbering plan.
636 Area Code FAQ
Where is area code 636?
Area code 636 is located in Missouri, primarily serving O'Fallon and surrounding cities including Saint Charles, Wentzville, Chesterfield. The region operates on CT (America/Chicago) time.
What state is 636 area code?
636 is a Missouri area code. It was put into service in 1999 and has no overlay codes — it covers its geographic area exclusively.
Is 636 a scam area code?
636 is a legitimate North American area code allocated by NANPA to Missouri. Like any geographic area code, scammers sometimes spoof 636 numbers — judge each call by content (urgent demands, unfamiliar transfers) rather than the area code alone. Run the specific number through our reverse lookup if you're unsure.
What time zone does 636 use?
Area code 636 operates on CT (America/Chicago). Numbers in this area code follow standard Missouri time-zone rules including any daylight-saving transitions for that region.
Can I look up a specific 636 phone number?
Yes. Use the reverse lookup widget above to enter a full 636 number. NumLocation returns the line type (mobile, landline, VoIP), carrier, rate-center city, and any public listings tied to the number — free.