ZIP Code 57751 — Keystone, SD
57751 is a standard (street delivery) ZIP code serving Keystone, South Dakota, in Pennington 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 57751 at a glance
| ZIP code | 57751 |
|---|---|
| Primary city | Keystone |
| State | South Dakota (SD) |
| County | Pennington FIPS 46103 |
| ZIP type | Standard (street delivery) |
| Time zone | America/Denver |
| Population | 893 |
| Coordinates | 43.867670, -103.423460 |
How ZIP+4 works in 57751
The four digits after the hyphen encode a delivery segment inside 57751. 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 57751 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 57751.
| ZIP | City | Distance |
|---|---|---|
| 57702 | Rapid City, SD | 11.4 mi |
| 57730 | Custer, SD | 14.5 mi |
| 57738 | Fairburn, SD | 20.3 mi |
| 57773 | Pringle, SD | 20.6 mi |
| 57745 | Hill City, SD | 20.6 mi |
| 57701 | Rapid City, SD | 20.6 mi |
| 57744 | Hermosa, SD | 20.8 mi |
| 57703 | Rapid City, SD | 21 mi |
| 57718 | Black Hawk, SD | 21.7 mi |
| 57759 | Nemo, SD | 25.2 mi |
| 57706 | Ellsworth Afb, SD | 25.7 mi |
| 57769 | Piedmont, SD | 26.7 mi |
Questions about 57751
What is the ZIP+4 code for 57751?
57751 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 57751, you need to look up a specific street address to get them.
What city is 57751?
57751 is assigned to Keystone, South Dakota, in Pennington 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.