ZIP Code 21001 — Aberdeen, MD
21001 is a standard (street delivery) ZIP code serving Aberdeen, Maryland, in Harford 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 21001 at a glance
| ZIP code | 21001 |
|---|---|
| Primary city | Aberdeen |
| State | Maryland (MD) |
| County | Harford FIPS 24025 |
| ZIP type | Standard (street delivery) |
| Time zone | America/New_York |
| Population | 27,168 |
| Coordinates | 39.510770, -76.202740 |
How ZIP+4 works in 21001
The four digits after the hyphen encode a delivery segment inside 21001. 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 21001 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 21001.
| ZIP | City | Distance |
|---|---|---|
| 21130 | Perryman, MD | 2.6 mi |
| 21017 | Belcamp, MD | 3.1 mi |
| 21028 | Churchville, MD | 4.5 mi |
| 21078 | Havre De Grace, MD | 5 mi |
| 21005 | Aberdeen Proving Ground, MD | 5.2 mi |
| 21015 | Bel Air, MD | 5.6 mi |
| 21009 | Abingdon, MD | 5.6 mi |
| 21040 | Edgewood, MD | 7.3 mi |
| 21902 | Perry Point, MD | 8 mi |
| 21014 | Bel Air, MD | 8.1 mi |
| 21085 | Joppa, MD | 9.3 mi |
| 21903 | Perryville, MD | 9.5 mi |
Questions about 21001
What is the ZIP+4 code for 21001?
21001 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 21001, you need to look up a specific street address to get them.
What city is 21001?
21001 is assigned to Aberdeen, Maryland, in Harford 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.