Massachusetts banks have additional deposit insurance that's on top of the FDIC insurance which allows your entire bank balance to be insured. This extra insurance is through a private insurance fund for MA banks called Deposit Insurance Fund or DIF.
Chris at Jumbo CD Investments has done some research on the history of DIF
. He noted that many MA banks lacked FDIC insurance until the 80's and had relied completely on DIF.
Note, there are a few MA banks that have DIF and accept deposits nationwide. However, some readers have noted that one should not consider the protection from DIF as equal to the FDIC protection.