| Locality | Post Code |
|---|---|
| Cheyenne River Reservation, Dewey | 57625 |
| Eagle Butte, Dewey | 57625 |
| Firesteel, Dewey | 57633 |
| Glencross, Dewey | 57630 |
| Isabel, Dewey | 57633 |
| La Plant, Dewey | 57652 |
| Lantry, Dewey | 57636 |
| Lightcap, Dewey | 57633 |
| Parade, Dewey | 57625 |
| Ridgeview, Dewey | 57652 |
| Standing Rock Reservation, Dewey | 57625 |
| Timber Lake, Dewey | 57656 |
| Whitehorse, Dewey | 57661 |