In 1731, Worcester County was created, which included the original town of Brookfield (incorporated in 1718 as part of Hampshire County). More territory was lost to Worcester County in 1742 when the town of Western (now Warren) was created and added to Worcester County. Further territorial losses occurred in 1749 when the towns of Enfield, Somers (split off from Enfield in 1734), and Suffield unilaterally joined Connecticut Colony. In 1761, Berkshire County was created resulting in even more territorial loss for Hampshire County. In 1811, Franklin County was split off from the northern part of Hampshire, and in the following year, Hampden County was split off from the southern part of Hampshire.
Franklin, Worcester, Hampden, and Berkshire counties.