The counties in the southeastern portion of the state retain county-level local government (Barnstable, Bristol, Dukes, Norfolk, Plymouth) or, in one case, (Nantucket County) consolidated city-county government.

The governments of Bristol, Plymouth, and Norfolk Counties remain substantially unchanged.

Dukes County in particular has a strong regional planning agency known as the Martha's Vineyard Commission.

[12] County seat is the standard term used in general communications by the Massachusetts government.

The Federal Information Processing Standard (FIPS) code, used by the United States government to uniquely identify counties, is provided with each entry.