Founded in 1748, Frederick County is one of 23 counties in the state of Maryland. Historically, Frederick County was formed from part of Prince George’s County. The city of Frederick is the county seat. With FIPS code of 21, Frederick County has a population of 279,835 and area of 667 square miles (1,728 km2).
List of all cities in Frederick County, MD alphabetically
| City/Town | Postal Code | Area Code |
| Adamstown, MD | 21710 | 301/240/227 |
| Braddock Heights, MD | 21714 | 301/240/227 |
| Brunswick, MD | 21716 | 301/240/227 |
| 21758 | 301/240/227 | |
| Buckeystown, MD | 21717 | 301/240/227 |
| Burkittsville, MD | 21718 | 301/240/227 |
| College Estates, MD | 21702 | 301/240/227 |
| Doubs, MD | 21710 | 301/240/227 |
| Emmitsburg, MD | 21727 | 301/240/227 |
| Fort Detrick, MD | 21702 | 301/240/227 |
| Frederick, MD | 21701 | 301/240/227 |
| 21702 | 301/240/227 | |
| 21703 | 301/240/227 | |
| 21704 | 301/240/227 | |
| 21705 | 301/240/227 | |
| 21709 | 301/240/227 | |
| Graceham, MD | 21788 | 301/240/227 |
| Hood College, MD | 21701 | 301/240/227 |
| Ijamsville, MD | 21754 | 301/240/227 |
| Jefferson, MD | 21755 | 301/240/227 |
| Knoxville, MD | 21716 | 301/240/227 |
| 21758 | 301/240/227 | |
| Ladiesburg, MD | 21759 | 301/240/227 |
| Lake Linganore, MD | 21774 | 301/240/227 |
| Lewistown, MD | 21701 | 301/240/227 |
| Libertytown, MD | 21762 | 301/240/227 |
| Middletown, MD | 21769 | 301/240/227 |
| Monrovia, MD | 21770 | 301/240/227 |
| Mount Airy, MD | 21771 | 301/240/227 |
| Myersville, MD | 21773 | 301/240/227 |
| New Market, MD | 21774 | 301/240/227 |
| New Midway, MD | 21775 | 301/240/227 |
| Point of Rocks, MD | 21777 | 301/240/227 |
| Rocky Ridge, MD | 21778 | 301/240/227 |
| Sabillasville, MD | 21780 | 301/240/227 |
| State Farm Ins Co, MD | 21709 | 301/240/227 |
| Thurmont, MD | 21788 | 301/240/227 |
| Tuscarora, MD | 21790 | 301/240/227 |
| Unionville, MD | 21792 | 301/240/227 |
| Urbana, MD | 21704 | 301/240/227 |
| Walkersville, MD | 21793 | 301/240/227 |
| Woodsboro, MD | 21798 | 301/240/227 |