ZIP Code 91737 — Rancho Cucamonga, CA
91737 is a standard (street delivery) ZIP code serving Rancho Cucamonga, California, in San Bernardino 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 91737 at a glance
| ZIP code | 91737 |
|---|---|
| Primary city | Rancho Cucamonga |
| State | California (CA) |
| County | San Bernardino FIPS 06071 |
| ZIP type | Standard (street delivery) |
| Time zone | America/Los_Angeles |
| Population | 22,958 |
| Coordinates | 34.155230, -117.578080 |
How ZIP+4 works in 91737
The four digits after the hyphen encode a delivery segment inside 91737. 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 91737 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.
Other ZIP codes in Rancho Cucamonga
Nearby ZIP codes
Showing the closest twelve. See every ZIP code within 25 miles of 91737.
| ZIP | City | Distance |
|---|---|---|
| 91701 | Rancho Cucamonga, CA | 1.7 mi |
| 91739 | Rancho Cucamonga, CA | 3.6 mi |
| 91730 | Rancho Cucamonga, CA | 3.8 mi |
| 91784 | Upland, CA | 4.7 mi |
| 91764 | Ontario, CA | 5.7 mi |
| 91786 | Upland, CA | 5.9 mi |
| 92358 | Lytle Creek, CA | 6.3 mi |
| 92336 | Fontana, CA | 6.8 mi |
| 92335 | Fontana, CA | 8 mi |
| 91711 | Claremont, CA | 8 mi |
| 91761 | Ontario, CA | 8.3 mi |
| 91763 | Montclair, CA | 8.9 mi |
Questions about 91737
What is the ZIP+4 code for 91737?
91737 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 91737, you need to look up a specific street address to get them.
What city is 91737?
91737 is assigned to Rancho Cucamonga, California, in San Bernardino 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.