Quabbin Reservoir is the largest body of water in Massachusetts, created between 1930 and 1940. It is the primary water supply for Boston. It has an aggregate capacity of 412 billion gallons (about 1.5 billion cubic meters). Water from the Quabbin flows to the Wachusett Reservoir by way of the Quabbin Aqueduct .

The reservoir was first proposed in the late 1890s, and funding for it was provided for by the state legislature in 1927. The Quabbin was formed by inundating the Swift River Valley , a drainage basin lying entirely within the state, by damming the river and a col that would otherwise have provided another outlet for its water.

The Quabbin's creation required the depopulation and thus the disincorporation, in April of 1938, of four towns: Dana, Enfield, Greenwich, and Prescott. (The latter three are the namesakes of of housing complexes at nearby Hampshire College.) Their land was annexed to surrounding municipalities. Thirty-six miles of railroad track was abandoned.

Despite the assumption of the full complement of buildings remaining intact though submerged, and the specific the myth of a church steeple whose tip becomes visible when the reservoir is relatively depleted, all buildings inside the shoreline were razed, and their flammable debris was burned nearby. The vegetation of the now submerged area was clear-cut and likewise burned. The outflow from the valley was stopped in 1939, and the reservoir filled and began supplying water in 1946.

Areas within the watershed but not inundated were likewise razed of structures and depopulated, for the protection of the quality of the water draining into the reservoir. Large portions of Dana are on higher ground, and its remains, predominantly cellar holes , can be visited as of 2005. Much of Prescott is also above water, on what is now known as the Prescott Peninsula, but it cannot be visited because of state restrictions. The center of what was once Prescott has been further leveled, for instance refilling cellar holes, to accommodate a radio telescope owned by the University of Massachusetts Amherst.