A map of the Massachusetts counties as they appeared between 1938 (when the Quabbin Reservoir was created) and 1947 (when the boundary between Essex and Middlesex counties was tweaked).
This file was derived from: Massachusetts county map, cb 500k.svg
Redrawn county lines informed by The Newberry Library
Original work by User:Awmcphee. This version by User:WallAdhesion.