County	Established	Original County(s)
Allegany	1789	Washington
Anne Arundel	1650	Original County
Baltimore City	1729	Baltimore County
Baltimore County	1659	Original County
Calvert	1654	Original County (formerly Patuxent)
Caroline	1773	Dorchester and Queen Anne's
Carroll	1837	Baltimore and Frederick
Cecil	1674	Kent
Charles	1658	Original County
Dorchester	1668	Original County
Frederick	1748	Prince George's
Garrett	1872	Allegany
Harford	1773	Baltimore
Howard	1851	Anne Arundel and Baltimore
Kent	1642	Original County
Montgomery	1776	Frederick
Prince George's	1695	Charles and Calvert
Queen Anne's	1706	Talbot
St. Mary's	1637	Original County
Somerset	1666	Original County
Talbot	1662	Kent
Washington	1776	Frederick
Wicomico	1867	Somerset and Worcester
Worcester	1742	Somerset