The Ash House was one of the oldest surviving structures of Rural Hill. It and the Well House were both built around 1788 during the same period that the Rural Hill Mansion was built. While the Well House kept water, the Ash House kept ashes from the fires built inside the home. A few times a year, the ashes were mixed with water and brought to a rolling boil. Animal fat, usually from pigs, was then added until the mixture reached a thick and mushy consistency. The mixture was then poured into wooden molds and allowed to cool, producing soap.