Allegany County	001	Cumberland	1789	Formed from part of Washington County.	From the Lenape Indian word oolikhanna, which means "beautiful stream"	Flag of Allegany County, Maryland.png	Seal of Allegany County, Maryland.png	74,012	430 sq mi
(1,114 km2)	State map highlighting Allegany County
Anne Arundel County	003	Annapolis	1650	Formed from part of St. Mary's County.	Anne Arundell was the maiden name of the wife of Cecil Calvert, 2nd Baron Baltimore. Between 1654 and 1658 it was known as Providence County by Puritan settlers	Flag of Anne Arundel County, Maryland.svg	Seal of Anne Arundel County, Maryland.png	550,488	588 sq mi
(1,523 km2)	State map highlighting Anne Arundel County
Baltimore County	005	Towson	1659	Formed from unorganized territory	Cecil Calvert, 2nd Baron Baltimore, first proprietor of the Maryland colony	Flag of Baltimore County, Maryland.svg	Seal of Baltimore County, Maryland.svg	817,455	682 sq mi
(1,766 km2)	State map highlighting Baltimore County
Baltimore City	510	Baltimore City	1851	Founded in 1729. Detached in 1851 from Baltimore County	Cecil Calvert, 2nd Baron Baltimore, first proprietor of the Maryland colony	Flag of Baltimore, Maryland.svg	Seal of Baltimore, Maryland.png	621,342	92 sq mi
(238 km2)	State map highlighting Baltimore City
Calvert County	009	Prince Frederick	1654	Formed as Patuxent County from unorganized territory. Renamed Calvert County in 1658	The Calvert family; prior to 1658 it was called Patuxent County, after the Patuxent Indians, a branch of the Algonquians	Flag of Calvert County, Maryland.svg	Link to image	89,628	345 sq mi
(894 km2)	State map highlighting Calvert County
Caroline County	011	Denton	1773	From parts of Dorchester County and Queen Anne's County	Lady Caroline Eden, daughter of Charles Calvert, 5th Baron Baltimore	Flag of Caroline County, Maryland.svg	Seal of Caroline County, Maryland.svg	32,718	326 sq mi
(844 km2)	State map highlighting Caroline County
Carroll County	013	Westminster	1837	From parts of Baltimore County and Frederick County	Charles Carroll of Carrollton, a representative to the Continental Congress and signatory of the Declaration of Independence	Flag of Carroll County, Maryland.png	Seal of Carroll County, Maryland.png	167,217	452 sq mi
(1,171 km2)	State map highlighting Carroll County
Cecil County	015	Elkton	1672	From parts of Baltimore County and Kent County	Cecil is an Anglicized form of the first name of Cecil Calvert, 2nd Baron Baltimore	 	Link to image	101,696	418 sq mi
(1,083 km2)	State map highlighting Cecil County
Charles County	017	La Plata	1658	From unorganized territory	Charles Calvert, 3rd Baron Baltimore, second proprietor of the Maryland colony	Flag of Charles County, Maryland.png	Link to image	150,592	643 sq mi
(1,665 km2)	State map highlighting Charles County
Dorchester County	019	Cambridge	1668	From unorganized territory	Dorchester in Dorset, England; the Earl of Dorset was a friend of the Calvert family	 	Link to image	32,551	540 sq mi
(1,399 km2)	State map highlighting Dorchester County
Frederick County	021	Frederick	1748	From part of Prince George's County	Frederick Calvert, 6th Baron Baltimore, final proprietor of the Maryland colony	Flag of Frederick County, Maryland.png	Seal of Frederick County, Maryland.png	239,582	667 sq mi
(1,728 km2)	State map highlighting Frederick County
Garrett County	023	Oakland	1872	From part of Allegany County	John Work Garrett, president of the Baltimore and Ohio Railroad	Flag of Garrett County, Maryland.svg	Seal of Garrett County, Maryland.svg	29,854	656 sq mi
(1,699 km2)	State map highlighting Garrett County
Harford County	025	Bel Air	1773	From part of Baltimore County	Henry Harford, illegitimate son of Frederick Calvert, 6th Baron Baltimore	Flag of Harford County, Maryland.png	Seal of Harford County, Maryland.svg	248,622	527 sq mi
(1,365 km2)	State map highlighting Harford County
Howard County	027	Ellicott City	1851	From parts of Anne Arundel County and Baltimore County	John Eager Howard, an American Revolutionary War officer and governor of Maryland	Flag of Howard County, Maryland.svg	Seal of Howard County, Maryland.png	299,430	254 sq mi
(658 km2)	State map highlighting Howard County
Kent County	029	Chestertown	1642	From unorganized territory	The English county of Kent	 	Link to image	20,191	414 sq mi
(1,072 km2)	State map highlighting Kent County
Montgomery County	031	Rockville	1776	From part of Frederick County	Richard Montgomery, an American Revolutionary War general	Flag of Montgomery County, Maryland.svg	Link to image	1,004,709	507 sq mi
(1,313 km2)	State map highlighting Montgomery County
Prince George's County	033	Upper Marlboro	1696	From parts of Calvert County and Charles County	Prince George of Denmark, the husband of Queen Anne of Great Britain	Flag of Prince George's County, Maryland.svg	Seal of Prince George's County, Maryland.svg	881,138	498 sq mi
(1,290 km2)	State map highlighting Prince George's County
Queen Anne's County	035	Centreville	1706	From parts of Talbot County	Anne, Queen of Great Britain	 	Link to image	48,595	510 sq mi
(1,321 km2)	State map highlighting Queen Anne's County
Saint Mary's County	037	Leonardtown	1637	From unorganized territory. Was named Potomac County between 1654 and 1658.	The Virgin Mary, first county named in a colony intended to be a haven for Catholics	 	Link to image	108,987	611 sq mi
(1,582 km2)	State map highlighting Saint Mary's County
Somerset County	039	Princess Anne	1666	From unorganized territory.	Mary, Lady Somerset, sister-in-law of Cecil Calvert, 2nd Baron Baltimore	Flag of Somerset County, Maryland.svg	Link to image	26,253	611 sq mi
(1,582 km2)	State map highlighting Somerset County
Talbot County	041	Easton	1662	From part of Kent County	Grace, Lady Talbot, sister of Cecil Calvert, 2nd Baron Baltimore	Flag of Talbot County, Maryland.svg	Link to image	38,098	477 sq mi
(1,235 km2)	State map highlighting Talbot County
Washington County	043	Hagerstown	1776	From part of Frederick County	George Washington, first President of the United States	Flag of Washington County, Maryland.svg	Link to image	149,180	468 sq mi
(1,212 km2)	State map highlighting Washington County
Wicomico County	045	Salisbury	1867	From parts of Somerset County and Worcester County	The Wicomico River; in Lenape, wicko mekee indicated "a place where houses are built," possibly in reference to a settlement	 	Link to image	100,647	400 sq mi
(1,036 km2)	State map highlighting Wicomico County
Worcester County	047	Snow Hill	1742	From part of Somerset County	Mary Arundell, the wife of Sir John Somerset, son of Henry Somerset, 1st Marquess of Worcester, and sister of Anne Arundell, the wife of Cecil Calvert, 2nd Baron Baltimore	Flag of Worcester County, Maryland.svg	Link to image	51,578	695 sq mi
(1,800 km2)	State map highlighting Worcester County