In England a long time ago someone important decided that the buildings should be made of brick and mortar instead of wood. In order to support the increased weight of the upper floors, wider walls were needed. To avoid significant loss of square footage on the lower lever because of thicker walls, “party walls” shared by neighbors were erected. Each neighbor had a duty to maintain the wall and to refrain from damaging the integrity of the “party wall.”
New England’s adoption of the “party walls” approach to fences and other such developments between property owners was the inspiration for Robert Frost’s poem, “Mending Wall,” which ends with, “Good fences make good neighbors.” (link)