Ottawa County Ohio (Vacant / Not In Use) has 4 places on the National Register of Historic Places including 1 place of Statewide significance. Significant places include Mo-John, Betsy, Cabin, Green Island Light, Island House, Wolcott, Benajah, House.
Some of the country's most noteable architects helped create the Ottawa County places including Henry Luckert, William Kelly and T.N. Graham. Prominent architectural styles found in Ottawa Country are Federal and Italianate.