As found on Archive.Org, several Community Shelter Plans existed for Massachusetts going into the late 1970’s.
The following links are for scanned copies of Community Shelter Plans for various counties in Massachusetts.
As I looked through some of them, I noticed that there are public shelters listed in some places that once had posted signs, and several others that were not believed to have ever had signs. That makes me wonder if, by the 1970’s, that officials wanted to let the public know which buildings might have been suitable as shelter, but did not make the effort to mark them with signs, or could not allocate signs to put on them. The lists also did not include all known shelters in an area, especially in larger cities and towns (i.e. Boston).
You might also notice that the maps with the shelter plans contain the disclaimer that these shelters were only for people whose basements were not suitable as shelters, and as well that not all shelters were stocked with food, and to bring whatever you could carry with you to the shelter.
An interesting read for anyone that lived in Massachusetts during this time, and maybe even remembers these documents being published or distributed.
Fallout Five Zero
Suffolk, Essex, and Middlesex Counties – Massachusetts (1979)
Barnstable, Bristol, Dukes, Nantucket, Norfolk, and Plymouth Counties – Massachusetts (1978)
Worcester County – Massachusetts (1978)
Berkshire, Franklin, Hampden, and Hampshire Counties – Massachusetts (1978)