Brimfield is a town in Hampden County, Massachusetts, United States. The population was 3,694 at the 2020 census. It is part of the Springfield, Massachusetts Metropolitan Statistical Area. Brimfield was first settled in 1706 and was officially incorporated in 1731. Until 1812, Brimfield was originally part of Hampshire County. The original Hampshire County i…Brimfield is a town in Hampden County, Massachusetts, United States. The population was 3,694 at the 2020 census. It is part of the Springfield, Massachusetts Metropolitan Statistical Area. Brimfield was first settled in 1706 and was officially incorporated in 1731. Until 1812, Brimfield was originally part of Hampshire County. The original Hampshire County included territory that is now in modern-day Hampden County, Franklin County, and Berkshire County as well as small parts of modern-day Worcester County.