Where in Massachusetts can I buy pottery clay?

well, it really depends where in MA you live, I am sure it takes more than 1 hour to drive from one end to the other...
but there are the addresses of the distributors for laguna clay, maybe one is close to you: http://www.lagunaclay.com/distributors/#…
Otherwise I'd look if there are pottery studios or stores for ceramics in your area consulting the yellow pages. Either should carry a range of different clays.