| | Allegany County | MD | 24001 | | Cumberland, MD-WV 19060 | | Central | metro county (urban) | federal/state
government-dependent | https://maps.google.com/?q=AlleganyCounty+MD |
| | Anne Arundel County | MD | 24003 | | Baltimore-Columbia-Towson,
MD 12580 | Washington-Baltimore-Arlington,
DC-MD-VA-WV-PA 548 | Central | metro county (urban) | federal/state
government-dependent | https://maps.google.com/?q=AnneArundelCounty+MD |
| | Baltimore County | MD | 24005 | | Baltimore-Columbia-Towson,
MD 12580 | Washington-Baltimore-Arlington,
DC-MD-VA-WV-PA 548 | Central | metro county (urban) | nonspecialized | https://maps.google.com/?q=BaltimoreCounty+MD |
| | Calvert County | MD | 24009 | | Lexington Park, MD 30500 | Washington-Baltimore-Arlington,
DC-MD-VA-WV-PA 548 | Central | metro county (urban) | recreation | https://maps.google.com/?q=CalvertCounty+MD |
| | Caroline County | MD | 24011 | | | | | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=CarolineCounty+MD |
| | Carroll County | MD | 24013 | | Baltimore-Columbia-Towson,
MD 12580 | Washington-Baltimore-Arlington,
DC-MD-VA-WV-PA 548 | Outlying | metro county (urban) | nonspecialized | https://maps.google.com/?q=CarrollCounty+MD |
| | Dorchester County | MD | 24019 | | Cambridge, MD 15700 | Washington-Baltimore-Arlington,
DC-MD-VA-WV-PA 548 | Central | nonmetro county (rural) | nonspecialized | https://maps.google.com/?q=DorchesterCounty+MD |
| | Garrett County | MD | 24023 | | | | | nonmetro county (rural) | recreation | https://maps.google.com/?q=GarrettCounty+MD |
| | Harford County | MD | 24025 | | Baltimore-Columbia-Towson,
MD 12580 | Washington-Baltimore-Arlington,
DC-MD-VA-WV-PA 548 | Outlying | metro county (urban) | federal/state
government-dependent | https://maps.google.com/?q=HarfordCounty+MD |
| | Howard County | MD | 24027 | | Baltimore-Columbia-Towson,
MD 12580 | Washington-Baltimore-Arlington,
DC-MD-VA-WV-PA 548 | Central | metro county (urban) | nonspecialized | https://maps.google.com/?q=HowardCounty+MD |