Most cultural landscapes of the harbor islands are characterized as "historic vernacular," meaning that they were imprinted by the settlement, customs, and everyday use of people who altered the physical, biological, and cultural character of their surroundings. Fields and forests once inhabited by American Indians were later used as Euro-American farms and pastures, that, when abandoned, were transformed through natural succession into stands of trees, shrubs, vines, and herbaceous vegetation. On Middle Brewster and Calf islands the stone walls, house foundations, and remnants of gardens still demarcate the summer communities that thrived prior to World War I. On Grape Island a farmhouse foundation and a lone willow tree remain, while horse pastures abandoned during World War II have reverted to tree cover. The past agricultural use of Thompson Island is still evident in the landscape.
Many islands may also have "ethnographic landscapes," those containing natural and cultural resources that associated people define as "heritage resources" such as contemporary settlements, subsistence communities, and burial grounds. Such places can be found on Peddocks, Deer, Long, the Brewsters, and many other islands. The community of summer cottages on Peddocks Island, previously a fishing village, has been in active use for nearly 100 years. The islands were once seasonal homes for Indians. Deer Island and other islands became the location of tragic imprisonment of who were held during King Philip's War. (See "Native Americans and the Islands".)
A surprising number of harbor islands and associated peninsulas contain "historic designed landscapes," those consciously laid out by a landscape gardener, architect, or horticulturist according to design principles or by others in a recognized style or tradition. These are seen notably in the Olmsted design at Worlds End and in vestiges of military landscape design on several islands. Many island landscapes are also recognized as "historic sites," those places associated with a historic activity, event, or person. Such sites include the lighthouses on Little Brewster, where the landscape portrays the lifestyle of keepers who have tended the light for nearly 300 years, and on The Graves and Long Island.