According to the United States Census Bureau, the town has a total area of 58.6 square miles (151.9 km²), of which 44.8 square miles (116.0 km²) is land and 13.9 square miles (36.0 km²), or 23.69%, is water.
Because of the lands of the Prescott Peninsula, New Salem is the largest town by area in Franklin County and the largest community by area in western Massachusetts (Hampden, Hampshire, Franklin, and Berkshire counties).
It is the twenty-first largest of 351 cities and towns in the Commonwealth.
New Salem's modern southern town lines are dictated by the former West and Middle Branches of the Swift River, which are now submerged as part of the Quabbin Reservoir.
The land of the two forks of the reservoir is now known as the Prescott Peninsula, containing the highest points in town, at Mount Pleasant and Prescott Hill (the latter of which was part of Pelham).
The town owns several islands in the reservoir as well, including those around Russ Mountain and Mount L. Much of the original town land was high ground, sloping down eastward towards the marshes near Lake Rohunta, along the Athol town line.
A small section of state forest is located near this lake, with other small sections scattered in the western part of the former town.

New Salem lies at the southeastern corner of Franklin Valley, with its lands extending southward between Hampshire County and Worcester County.
 The town is bordered by Orange to the north, Athol to the northeast, Petersham to the east, Ware to the south, Belchertown to the southeast, and Pelham, Shutesbury and Wendell to the west.
Because of the reservoir, there is no land link between New Salem and Pelham, Belchertown or Ware.
From the town common, New Salem lies 19 miles (31 km) east-southeast of the county seat of Greenfield, 35 miles (56 km) north-northeast of Springfield, 40 miles (64 km) northwest of Worcester and 75 miles (121 km) west of Boston.
According to the United States Census Bureau, the town has a total area of 58.6 square miles (151.9 km²), of which 44.8 square miles (116.0 km²) is land and 13.9 square miles (36.0 km²), or 23.69%, is water. Because of the lands of the Prescott Peninsula, New Salem is the largest town by area in Franklin County and the largest community by area in western Massachusetts (Hampden, Hampshire, Franklin, and Berkshire counties). It is the twenty-first largest of 351 cities and towns in the Commonwealth. New Salem's modern southern town lines are dictated by the former West and Middle Branches of the Swift River, which are now submerged as part of the Quabbin Reservoir. The land of the two forks of the reservoir is now known as the Prescott Peninsula, containing the highest points in town, at Mount Pleasant and Prescott Hill (the latter of which was part of Pelham). The town owns several islands in the reservoir as well, including those around Russ Mountain and Mount L. Much of the original town land was high ground, sloping down eastward towards the marshes near Lake Rohunta, along the Athol town line. A small section of state forest is located near this lake, with other small sections scattered in the western part of the former town.
New Salem lies at the southeastern corner of Franklin Valley, with its lands extending southward between Hampshire County and Worcester County.  The town is bordered by Orange to the north, Athol to the northeast, Petersham to the east, Ware to the south, Belchertown to the southeast, and Pelham, Shutesbury and Wendell to the west. Because of the reservoir, there is no land link between New Salem and Pelham, Belchertown or Ware. From the town common, New Salem lies 19 miles (31 km) east-southeast of the county seat of Greenfield, 35 miles (56 km) north-northeast of Springfield, 40 miles (64 km) northwest of Worcester and 75 miles (121 km) west of Boston.
New Salem, Massachusetts