New Salem was first settled in 1737 and was officially incorporated in 1753, named for the settlers from Salem that founded the town. New Salem benefited greatly by the building of the Quabbin Reservoir - though mostly geographically. Prior to its building, New Salem, which has always been the southeast corner of Franklin County, did not extend much further south than the village of Cooleyville, now along U.S. Route 202. However, with the forming of the reservoir, the town received all lands above the water line between the two forks of the reservoir, as it was the only land connection to the peninsula. With its southern borders now following former branches of the Swift River, New Salem now includes most of the former town of Prescott (except for a small corner east of the Middle Branch of the Swift River, which is now in Petersham), and parts of Greenwich and Enfield. (All of the northern half of Prescott had once belonged to New Salem; the southern half was originally part of Pelham, but was annexed to Prescott in the latter nineteenth century.) All the lands gained by the annexation were once part of Hampshire County.

Today most of the lands it gained are off-limits, protected as part of the Quabbin Reservation, which is administered by the Massachusetts Department of Conservation & Recreation (DCR). The Five College Radio Astronomy Observatory, until 2011, lay along what was once the Prescott-Greenwich town line, and researchers from the Five Colleges were allowed access to it. Additionally, members of the Swift River Historical Society take a yearly tour of the area in the peninsula by bus. No other access is permitted.

...
Wikipedia