| 21005 Aber Prov Grd | 410/443/667 | Harford County | Maryland (MD) |
| 21010 Aber Prov Grd | 410/443/667 | Harford County | Maryland (MD) |
| 21001 Aberdeen | 410/443/667 | Harford County | Maryland (MD) |
| 21005 Aberdeen Proving Ground | 410/443/667 | Harford County | Maryland (MD) |
| 21010 Aberdeen Proving Ground | 410/443/667 | Harford County | Maryland (MD) |
| 21009 Abingdon | 410/443/667 | Harford County | Maryland (MD) |
| 21005 APG | 410/443/667 | Harford County | Maryland (MD) |
| 21014 Bel Air | 410/443/667 | Harford County | Maryland (MD) |
| 21015 Bel Air | 410/443/667 | Harford County | Maryland (MD) |
| 21017 Belcamp | 410/443/667 | Harford County | Maryland (MD) |
| 21018 Benson | 410/443/667 | Harford County | Maryland (MD) |
| 21160 Cardiff | 410/443/667 | Harford County | Maryland (MD) |
| 21028 Churchville | 410/443/667 | Harford County | Maryland (MD) |
| 21034 Darlington | 410/443/667 | Harford County | Maryland (MD) |
| 21040 Edgewood | 410/443/667 | Harford County | Maryland (MD) |
| 21010 Edgewood Arsenal | 410/443/667 | Harford County | Maryland (MD) |
| 21047 Fallston | 410/443/667 | Harford County | Maryland (MD) |
| 21050 Forest Hill | 410/443/667 | Harford County | Maryland (MD) |
| 21010 Gunpowder | 410/443/667 | Harford County | Maryland (MD) |
| 21078 Havre de Grace | 410/443/667 | Harford County | Maryland (MD) |
| 21078 Hvre de Grace | 410/443/667 | Harford County | Maryland (MD) |
| 21084 Jarrettsville | 410/443/667 | Harford County | Maryland (MD) |
| 21085 Joppa | 410/443/667 | Harford County | Maryland (MD) |
| 21085 Joppatown | 410/443/667 | Harford County | Maryland (MD) |
| 21085 Joppatowne | 410/443/667 | Harford County | Maryland (MD) |
| 21085 Magnolia | 410/443/667 | Harford County | Maryland (MD) |
| 21161 Norrisville | 410/443/667 | Harford County | Maryland (MD) |
| 21130 Perryman | 410/443/667 | Harford County | Maryland (MD) |
| 21132 Pylesville | 410/443/667 | Harford County | Maryland (MD) |
| 21017 Riverside | 410/443/667 | Harford County | Maryland (MD) |
| 21154 Street | 410/443/667 | Harford County | Maryland (MD) |
| 21161 White Hall | 410/443/667 | Harford County | Maryland (MD) |
| 21160 Whiteford | 410/443/667 | Harford County | Maryland (MD) |