Completed in 1865, this home was the vacation retreat of Jay Cooke and his family. Known as the "financier" for the Union states during the Civil War, Cooke organized a program to sell millions of dollars worth of bonds to support the war effort. The house is of a high Victorian Italianate mode with a Gothic style tower topped with crenellations. Distinctive hood moldings outline windows and over-scaled and ornamental brackets support crowning cornices. The house, commonly known as Cooke Castle, hosted many notables of the time, including William T. Sherman, William Howard Taft, Rutherford B. Hayes, Salmon Chase and John Brown, Jr. Born in Sandusky in 1821, Cooke, an avid fisherman, acquired the island for $3,001 in 1864. University trustee Julius Stone gave the island to The Ohio State University in 1925. The house was placed on the National Register of Historic Landmarks in 1966.