| Locality | Post Code |
|---|---|
| Clayton, Clayton | 52049 |
| Colesburg, Clayton | 52035 |
| Communia, Clayton | 52043 |
| Edgewood, Clayton | 52042 |
| Elgin, Clayton | 52141 |
| Elkader, Clayton | 52043 |
| Elkport, Clayton | 52044 |
| Farmersburg, Clayton | 52047 |
| Froelich, Clayton | 52047 |
| Garber, Clayton | 52048 |
| Garnavillo, Clayton | 52049 |
| Giard, Clayton | 52157 |
| Guttenberg, Clayton | 52052 |
| Hardin, Clayton | 52156 |
| Holy Cross, Clayton | 52053 |
| Littleport, Clayton | 52042 |
| Luana, Clayton | 52156 |
| Marquette, Clayton | 52158 |
| McGregor, Clayton | 52157 |
| Mederville, Clayton | 52043 |
| Millville, Clayton | 52052 |
| Monona, Clayton | 52159 |
| National, Clayton | 52047 |
| North Buena Vista, Clayton | 52066 |
| Osborne, Clayton | 52043 |
| Postville, Clayton | 52162 |