| Locality | Post Code |
|---|---|
| Adamstown, Frederick | 21710 |
| Braddock Heights, Frederick | 21714 |
| Brunswick, Frederick | 21716 |
| Buckeystown, Frederick | 21717 |
| Burkittsville, Frederick | 21718 |
| College Estates, Frederick | 21702 |
| Doubs, Frederick | 21710 |
| Emmitsburg, Frederick | 21727 |
| Fort Detrick, Frederick | 21702 |
| Frederick, Frederick | 21701, 21702, 21703, 21704 |
| Graceham, Frederick | 21788 |
| Hood College, Frederick | 21701 |
| Ijamsville, Frederick | 21754 |
| Jefferson, Frederick | 21755 |
| Knoxville, Frederick | 21758 |
| Ladiesburg, Frederick | 21759 |
| Lake Linganore, Frederick | 21774 |
| Lewistown, Frederick | 21701 |
| Libertytown, Frederick | 21762 |
| Middletown, Frederick | 21769 |
| Monrovia, Frederick | 21770 |
| Mount Airy, Frederick | 21771 |
| Myersville, Frederick | 21773 |
| New Market, Frederick | 21774 |
| New Midway, Frederick | 21775 |
| Point of Rocks, Frederick | 21777 |