Benjamin Franklin Allen, Iowa’s first millionaire, built Terrace Hill as his family home. Construction of this 18,000-square-foot home began in 1866 and was completed in 1869. The original cost of $250,000 included the Mansion, Carriage House, all of the furnishings, and approximately 30 acres of land. The house contained very modern features for its time, such as hot and cold running water, gas lights, a lift, and indoor restrooms.