Middleton is a town in Essex County, Massachusetts, United States. The population was 9,779 at the 2020 census. Before European colonial settlement, the area was home to a number of native settlements. The area fell along an ill-defined "border" region between the Massachusett and Pennacook. The tribes in this region generally spoke the Abenakā¦Middleton is a town in Essex County, Massachusetts, United States. The population was 9,779 at the 2020 census. Before European colonial settlement, the area was home to a number of native settlements. The area fell along an ill-defined "border" region between the Massachusett and Pennacook. The tribes in this region generally spoke the Abenaki language, with major local tribes being the Naumkeag and Agawam. Will's Hill in modern-day Middleton was home to a winter village founded by an Algonquin Sachem.