There are dozens of electrical suppliers in Massachusetts.
Northeast Electrical Distributors/Ralph Pill
Rexel/CLS
Electrical Wholesalers
Granite City Electric (don't go to them unless you have several first born children to give away)
Yale Electric
Graybar
These are the major regional/national chain suppliers in the area.
Northeast is good, and their distribution center is in Canton, MA.
Rexel/CLS is also good.
EW - way to go IMHO, usually have anything you need in a day.
Granite City will not only cost more, but from my experience, if you have anything delivered from a phone order, it will take two or three times for them to get it right. At least out of the Hartford branch, can't comment on MA branches.
Yale - no experience
Graybar - no respect given to a "premier Square D distributor" that doesn't stock a 15 amp Homeline arc-fault, or at least they didn't when I went to get some. Same with a 2 pole 20 amp breaker one time.