ZIP Code 91789 — Walnut, CA
91789 is a standard (street delivery) ZIP code serving Walnut, California, in Los Angeles 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 91789 at a glance
| ZIP code | 91789 |
|---|---|
| Primary city | Walnut |
| State | California (CA) |
| County | Los Angeles FIPS 06037 |
| ZIP type | Standard (street delivery) |
| Time zone | America/Los_Angeles |
| Population | 40,298 |
| Coordinates | 34.018580, -117.854080 |
How ZIP+4 works in 91789
The four digits after the hyphen encode a delivery segment inside 91789. 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 91789 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 91789.
| ZIP | City | Distance |
|---|---|---|
| 91792 | West Covina, CA | 2.7 mi |
| 91765 | Diamond Bar, CA | 3.1 mi |
| 91791 | West Covina, CA | 3.7 mi |
| 91748 | Rowland Heights, CA | 3.9 mi |
| 91724 | Covina, CA | 4.3 mi |
| 91768 | Pomona, CA | 4.8 mi |
| 91744 | La Puente, CA | 4.8 mi |
| 91723 | Covina, CA | 4.9 mi |
| 91766 | Pomona, CA | 5.8 mi |
| 91790 | West Covina, CA | 5.9 mi |
| 92821 | Brea, CA | 6.2 mi |
| 91722 | Covina, CA | 6.2 mi |
Questions about 91789
What is the ZIP+4 code for 91789?
91789 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 91789, you need to look up a specific street address to get them.
What city is 91789?
91789 is assigned to Walnut, California, in Los Angeles 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.