It's not for every station but try
http://www.bostonradio.org
and look for the descriptions of each station
with info on history,calls,formats. Look for Station Profiles.
I know I saw something along the lines of this for Pittsburgh))
(Example
http://www.pbrtv.com/stations/pittsburgh-area-stations/pittsburgh-area-am-stations/ ) where pbrtv.com has rundowns of the history of
local AM,FM,and TV outlets.Something like that
would be good here but as I say try bostonradio.org