ZIP Code 21723 — Cooksville, MD
21723 is a standard (street delivery) ZIP code serving Cooksville, Maryland, in Howard 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 21723 at a glance
| ZIP code | 21723 |
|---|---|
| Primary city | Cooksville |
| State | Maryland (MD) |
| County | Howard FIPS 24027 |
| ZIP type | Standard (street delivery) |
| Time zone | America/New_York |
| Population | 669 |
| Coordinates | 39.328250, -77.010560 |
How ZIP+4 works in 21723
The four digits after the hyphen encode a delivery segment inside 21723. 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 21723 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 21723.
| ZIP | City | Distance |
|---|---|---|
| 21794 | West Friendship, MD | 2.9 mi |
| 21797 | Woodbine, MD | 3.2 mi |
| 21738 | Glenwood, MD | 3.4 mi |
| 21737 | Glenelg, MD | 5.1 mi |
| 21784 | Sykesville, MD | 5.4 mi |
| 21104 | Marriottsville, MD | 5.8 mi |
| 21036 | Dayton, MD | 6.5 mi |
| 21042 | Ellicott City, MD | 7.4 mi |
| 21163 | Woodstock, MD | 8.2 mi |
| 20833 | Brookeville, MD | 8.8 mi |
| 21029 | Clarksville, MD | 9 mi |
| 21771 | Mount Airy, MD | 9.2 mi |
Questions about 21723
What is the ZIP+4 code for 21723?
21723 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 21723, you need to look up a specific street address to get them.
What city is 21723?
21723 is assigned to Cooksville, Maryland, in Howard 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.