Finding attorneys who are members of the Massachusetts bar is a simple process. Simply go to the Massachusetts Board of Bar Overseers' website and perform a search. Other states' bars should have similar directories as well. (And yes, despite its dated look, this page is part of the current site.)
This page maintained by the Massachusetts Board of Bar Overseers provides an alphabetical listing of every state agency, along with links to their websites. This is a useful tool if you are trying to find which agency is relevant for your legal research, which is unfortunately not always obvious from the outset.