ZIP Code 63366 — O'fallon, MO
63366 is a standard (street delivery) ZIP code serving O'fallon, Missouri, in St. Charles County. To mail something here you only need these five digits — but the four-digit extension narrows delivery to a single point, and it is what USPS bulk postage discounts are priced on.
ZIP code 63366 at a glance
| ZIP code | 63366 |
|---|---|
| Primary city | O'fallon |
| State | Missouri (MO) |
| County | St. Charles FIPS 29183 |
| ZIP type | Standard (street delivery) |
| Time zone | America/Chicago |
| Population | 54,769 |
| Coordinates | 38.859180, -90.719640 |
How ZIP+4 works in 63366
The four digits after the hyphen encode a delivery segment inside 63366. In practice one segment usually means:
- One side of one block — odd numbers on a street between two cross streets
- A single large building, or one floor of it
- A group of PO boxes, sometimes a single box
- A single business that receives enough mail to warrant its own code
That is why 63366 has no single ZIP+4: two neighbors across the street from each other usually have different ones. Enter a street address above and we will return the exact nine-digit code along with the standardized USPS address format.
Other ZIP codes in O'fallon
Nearby ZIP codes
Showing the closest twelve. See every ZIP code within 25 miles of 63366.
| ZIP | City | Distance |
|---|---|---|
| 63369 | Old Monroe, MO | 6.2 mi |
| 63367 | Lake Saint Louis, MO | 6.9 mi |
| 63376 | Saint Peters, MO | 6.9 mi |
| 63368 | O'fallon, MO | 7.4 mi |
| 62036 | Golden Eagle, IL | 8 mi |
| 63385 | Wentzville, MO | 8.5 mi |
| 63389 | Winfield, MO | 10 mi |
| 63362 | Moscow Mills, MO | 10.1 mi |
| 63304 | Saint Charles, MO | 10.7 mi |
| 62013 | Brussels, IL | 11 mi |
| 63303 | Saint Charles, MO | 12.6 mi |
| 63348 | Foristell, MO | 12.8 mi |
Questions about 63366
What is the ZIP+4 code for 63366?
63366 is the five-digit ZIP code. The ZIP+4 adds four more digits that identify a specific delivery point — usually one side of a city block, a single building, or a group of PO boxes. Because those four digits change from address to address within 63366, you need to look up a specific street address to get them.
What city is 63366?
63366 is assigned to O'fallon, Missouri, in St. Charles County.
Do I need to use the ZIP+4?
It is optional for ordinary mail, but it speeds up sorting and it is required for most USPS bulk-mail postage discounts. Many address-verification and e-commerce systems also use ZIP+4 to confirm a delivery point exists.
Need thousands of these?
Upload a CSV and get ZIP+4, county, carrier route, and delivery-point data appended to every row — or call the API directly.