| Locality | Post Code |
|---|---|
| Annapolis Junction, Howard | 20701 |
| Clarksville, Howard | 21029 |
| Columbia, Howard | 21044, 21045, 21046 |
| Cooksville, Howard | 21723 |
| Daniels, Howard | 21043 |
| Dayton, Howard | 21036 |
| Elkridge, Howard | 21075 |
| Ellicott, Howard | 21042, 21029 |
| Ellicott City, Howard | 21041, 21042, 21043 |
| Fulton, Howard | 20759 |
| Glenelg, Howard | 21737 |
| Glenwood, Howard | 21738 |
| Granite, Howard | 21163 |
| Highland, Howard | 20777 |
| Ilchester, Howard | 21043 |
| Jessup, Howard | 20794 |
| Laurel, Howard | 20723 |
| Lisbon, Howard | 21765 |
| Marriottsville, Howard | 21104 |
| Oella, Howard | 21043 |
| Savage, Howard | 20763 |
| Scaggsville, Howard | 20723 |
| Simpsonville, Howard | 21150 |
| West Friendship, Howard | 21794 |
| Woodbine, Howard | 21797 |
| Woodstock, Howard | 21163 |