ZIP Code 57278 — Willow Lake, SD
57278 is a standard (street delivery) ZIP code serving Willow Lake, South Dakota, in Clark 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 57278 at a glance
| ZIP code | 57278 |
|---|---|
| Primary city | Willow Lake |
| State | South Dakota (SD) |
| County | Clark FIPS 46025 |
| ZIP type | Standard (street delivery) |
| Time zone | America/Chicago |
| Population | 1,011 |
| Coordinates | 44.646890, -97.682270 |
How ZIP+4 works in 57278
The four digits after the hyphen encode a delivery segment inside 57278. 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 57278 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 57278.
| ZIP | City | Distance |
|---|---|---|
| 57271 | Vienna, SD | 9.7 mi |
| 57221 | Bryant, SD | 11.8 mi |
| 57322 | Carpenter, SD | 13.7 mi |
| 57225 | Clark, SD | 16.5 mi |
| 57233 | Erwin, SD | 16.8 mi |
| 57242 | Hazel, SD | 18.1 mi |
| 57386 | Yale, SD | 18.2 mi |
| 57231 | De Smet, SD | 19.4 mi |
| 57258 | Raymond, SD | 20.2 mi |
| 57353 | Iroquois, SD | 20.5 mi |
| 57243 | Henry, SD | 22.3 mi |
| 57241 | Hayti, SD | 23.1 mi |
Questions about 57278
What is the ZIP+4 code for 57278?
57278 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 57278, you need to look up a specific street address to get them.
What city is 57278?
57278 is assigned to Willow Lake, South Dakota, in Clark 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.