In order to determine the largest historic homes in each state, 24/7 Wall St. reviewed media sources, local and state historical societies, tourism boards, and the National Register of Historic Places. Only homes built before 1966 were considered. The buildings had to serve as single-family homes at some point in their history.
Most of these buildings no longer serve as homes, and many have been converted into museums. To be considered, the homes must have publicly available information about their size, or they provided that information to 24/7 Wall St. Houses were ranked on square footage, unless that information was unavailable, in which case the homes were ranked based on the number of rooms they have.