In April, 1991, architectural historian, Denys Peter Myers attributed the design of Hillforest to Isaiah Rogers. This attribution is based on journals kept by Rogers, which states that he came to Aurora, Indiana to design a house for a “Mr. Gaff” in 1853, and because the structure has similar characteristics with other works by Rogers. Born in 1800, Isaiah Rogers was from Massachusetts and was a student of the builder Solomon Willard. Rogers built Boston’s Tremont House, the first hotel with indoor plumbing, and the Astor House, a luxury hotel in New York City. He went on to design the Burnett House in Cincinnati, Ohio, which was the largest and most elegant hotel in the city. He also designed the Cathedral of the Assumption in Louisville, Kentucky, which had the highest spire at the time of 287 feet. Rogers eventually became the Supervising Architect of the United States from 1863 to 1865.
For Thomas Gaff, Rogers designed an Italian Renaissance Revival 2-story frame structure covered by a low-pitch hip roof. The facades are finished in wide cypress board siding with wooden quoin blocks at the corners. A semicircular section projects at the center of the main facade, rising to a belvedere (Italian for “beautiful view”) on the roof. A single-story porch extends across the full width of the facade, with a second story porch around the central projection. Windows are of full length, removing the need for doors to access the porches.