ZIP Code 21788 — Thurmont, MD
21788 is a standard (street delivery) ZIP code serving Thurmont, Maryland, in Frederick 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 21788 at a glance
| ZIP code | 21788 |
|---|---|
| Primary city | Thurmont |
| State | Maryland (MD) |
| County | Frederick FIPS 24021 |
| ZIP type | Standard (street delivery) |
| Time zone | America/New_York |
| Population | 11,654 |
| Coordinates | 39.594290, -77.419580 |
How ZIP+4 works in 21788
The four digits after the hyphen encode a delivery segment inside 21788. 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 21788 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.
Nearby ZIP codes
Showing the closest twelve. See every ZIP code within 25 miles of 21788.
| ZIP | City | Distance |
|---|---|---|
| 21778 | Rocky Ridge, MD | 4.6 mi |
| 21780 | Sabillasville, MD | 6.2 mi |
| 21798 | Woodsboro, MD | 7.4 mi |
| 21727 | Emmitsburg, MD | 8 mi |
| 21702 | Frederick, MD | 8.1 mi |
| 21773 | Myersville, MD | 8.1 mi |
| 21783 | Smithsburg, MD | 8.3 mi |
| 21793 | Walkersville, MD | 8.3 mi |
| 21757 | Keymar, MD | 8.5 mi |
| 21719 | Cascade, MD | 8.7 mi |
| 17214 | Blue Ridge Summit, PA | 11 mi |
| 21701 | Frederick, MD | 11.1 mi |
Questions about 21788
What is the ZIP+4 code for 21788?
21788 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 21788, you need to look up a specific street address to get them.
What city is 21788?
21788 is assigned to Thurmont, Maryland, in Frederick 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.