High Quality Content by WIKIPEDIA articles! The Town of Watertown is a city in Middlesex County, Massachusetts, United States. The population was 32,986 at the 2000 census. Watertown, first known as Saltonstall Plantation, was one of the earliest of the Massachusetts Bay settlements. It was begun early in 1630 by a group of settlers led by Sir Richard Saltonstall and the Rev. George Phillips and officially incorporated that same year. The alternate spelling "Waterton" is seen in some early documents. The first buildings were upon land now included within the limits of Cambridge known as Gerry's Landing. For its first quarter century Watertown ranked next to Boston in population and area. Since then its limits have been greatly reduced.