ZIP Code 21664 — Secretary, MD
21664 is a standard (street delivery) ZIP code serving Secretary, Maryland, in Dorchester 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 21664 at a glance
| ZIP code | 21664 |
|---|---|
| Primary city | Secretary |
| State | Maryland (MD) |
| County | Dorchester FIPS 24019 |
| ZIP type | Standard (street delivery) |
| Time zone | America/New_York |
| Population | 635 |
| Coordinates | 38.608100, -75.947320 |
How ZIP+4 works in 21664
The four digits after the hyphen encode a delivery segment inside 21664. 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 21664 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 21664.
| ZIP | City | Distance |
|---|---|---|
| 21631 | East New Market, MD | 1.4 mi |
| 21643 | Hurlock, MD | 4.8 mi |
| 21835 | Linkwood, MD | 5.2 mi |
| 21673 | Trappe, MD | 5.9 mi |
| 21659 | Rhodesdale, MD | 8.3 mi |
| 21655 | Preston, MD | 9.6 mi |
| 21613 | Cambridge, MD | 10.3 mi |
| 21654 | Oxford, MD | 11.2 mi |
| 21632 | Federalsburg, MD | 12.2 mi |
| 21869 | Vienna, MD | 12.5 mi |
| 21861 | Sharptown, MD | 12.8 mi |
| 21837 | Mardela Springs, MD | 14.1 mi |
Questions about 21664
What is the ZIP+4 code for 21664?
21664 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 21664, you need to look up a specific street address to get them.
What city is 21664?
21664 is assigned to Secretary, Maryland, in Dorchester 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.