County	Date  Formed	Parent County	County Seat
Barnstable	1685	New Plymouth Colony	Barnstable
Berkshire	1761	Hampshire	Pittsfield
Bristol	1685	New Plymouth Colony	Taunton
Dukes	1683	none	Edgartown
Essex	1643	none	Lawrence, Newburyport, Salem
Franklin	1811	Hampshire	Greenfield
Hampden	1812	Hampshire	Springfield
Hampshire	1662	Middlesex	Northampton
Middlesex	1643	none	Cambridge, Lowell
Nantucket	1695	none	Nantucket
Norfolk	1793	Suffolk	Dedham
Plymouth	1685	New Plymouth Colony	Plymouth
Suffolk	1643	none	Boston
Worcester	1731	Suffolk, Middlesex	Worcester