Allegany County (1789 - Present)
Anne Arundel County (1650 - Present)
Baltimore City (1851 - Present)
Baltimore County (1660 - Present)
Calvert County (1654 - Present)
Caroline County (1774 - Present)
Carroll County (1836 - Present)
Cecil County (1674 - Present)
Charles County (1658 - Present)
Charles County Original (1650 - 1654)
Dorchester County (1669 - Present)
Durham County (1669 - 1672)
Frederick County (1748 - Present)
Garrett County (1872 - Present)
Harford County (1774 - Present)
Howard County (1851 - Present)
Kent County (1642 - Present)
Montgomery County (1776 - Present)
Prince Georges County (1696 - Present)
Queen Annes County (1707 - Present)
Somerset County (1666 - Present)
St Marys County (1638 - Present)
Talbot County (1662 - Present)
Washington County (1776 - Present)
Wicomico County (1867 - Present)
Worcester County (1742 - Present)
Worcester County Original (1672 - 1685)