ZIP Code 91901 — Alpine, CA
91901 is a standard (street delivery) ZIP code serving Alpine, California, in San Diego 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 91901 at a glance
| ZIP code | 91901 |
|---|---|
| Primary city | Alpine |
| State | California (CA) |
| County | San Diego FIPS 06073 |
| ZIP type | Standard (street delivery) |
| Time zone | America/Los_Angeles |
| Population | 18,197 |
| Coordinates | 32.814670, -116.719290 |
How ZIP+4 works in 91901
The four digits after the hyphen encode a delivery segment inside 91901. 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 91901 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 91901.
| ZIP | City | Distance |
|---|---|---|
| 91931 | Guatay, CA | 8.2 mi |
| 91916 | Descanso, CA | 8.4 mi |
| 91935 | Jamul, CA | 8.7 mi |
| 92021 | El Cajon, CA | 9.1 mi |
| 92019 | El Cajon, CA | 9.2 mi |
| 92040 | Lakeside, CA | 11.7 mi |
| 91917 | Dulzura, CA | 13 mi |
| 91963 | Potrero, CA | 13.5 mi |
| 91962 | Pine Valley, CA | 13.9 mi |
| 92020 | El Cajon, CA | 14.6 mi |
| 91978 | Spring Valley, CA | 14.7 mi |
| 91948 | Mount Laguna, CA | 15 mi |
Questions about 91901
What is the ZIP+4 code for 91901?
91901 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 91901, you need to look up a specific street address to get them.
What city is 91901?
91901 is assigned to Alpine, California, in San Diego 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.