Hatfield doesn't have a formal historical society, but does have a very tight concentration of late 1600/early 1700 houses in what is called the Elm Street Historic District
made up of Elm, Sunset, and Scotland Sts., Little Neponset Rd.
Take exit 29 off I91N, right off the ramp is Elm. st. follow for about 2 miles and you will start to see some amazingly old and very well kept houses on both sids of the street. Most have dates proudly placarded on them.
The town is small and close knit; stopping pretty much anyone in town just may yield an hour long conversation about local history. In the summer, everyone is sitting out on their porches.
When on Chestnut st., note the very impressive Sycamore tree of about 48" in diameter standing in front of a very nice early 1700's home.
I took down an old tobacco barn on Elm st. this past fall and had a great time there, even met the 80-something year old guy who replaced the roof on the barn after the 38 Hurricane came and took it off!
feel free to email me direct to talk more if you wish.
Have fun!
shaun