| Zip Code | City | Population ↓ |
|---|---|---|
| 21702 | Frederick | 46,596 |
| 21701 | Frederick | 40,787 |
| 21703 | Frederick | 39,606 |
| 21771 | Mount Airy | 31,653 |
| 21704 | Frederick | 18,473 |
| 21774 | New Market | 15,096 |
| 21769 | Middletown | 12,562 |
| 21788 | Thurmont | 11,412 |
| 21793 | Walkersville | 10,882 |
| 21770 | Monrovia | 7,786 |
| 21754 | Ijamsville | 7,260 |
| 21716 | Brunswick | 6,630 |
| 21727 | Emmitsburg | 6,588 |
| 21755 | Jefferson | 5,706 |
| 21773 | Myersville | 5,553 |
| 21710 | Adamstown | 4,988 |
| 21791 | Union Bridge | 4,855 |
| 21758 | Knoxville | 4,610 |
| 21798 | Woodsboro | 2,699 |
| 21777 | Point Of Rocks | 2,360 |
| 21780 | Sabillasville | 1,975 |
| 21778 | Rocky Ridge | 880 |
| 21714 | Braddock Heights | 272 |
| 21717 | Buckeystown | 209 |
| 21762 | Libertytown | 176 |
| 21718 | Burkittsville | 143 |
| 21705 | Frederick | 5 |
| 21790 | Tuscarora | 0 |
The data shown reflect ZCTAs from the US Census. As of 2024, there are 28 ZCTAs in Frederick County, Maryland (US Census).