This thirteen-sided barn is a variation of the round barn, a type of farm building that was less common in New York because it was harder to build than traditional Dutch and English barns. Leonard Bronk, Jr., one of the most prosperous farmers in Greene County, probably built it as an innovative way to store hay during a time when hay was the farm’s major cash crop and much of it was shipped to New York City to feed its growing horse population. Its design was better suited to loose hay storage than rectangular or square barns, whose sharp corners could trap hay and make it difficult to remove. The barn once had a long rectangular extension on the northwest side, but it deteriorated and was removed in the 1960s. The seventy foot diameter structure has thirteen side panels and thirteen triangular roof sections, with framing that generally resembles an open umbrella. A single nine inch pole rises from the center of the lower level to the top of the cupola, probably important during construction but serving no structural purpose. The side panels are tied together at the top by thirteen squinches that form a rigid load-bearing wooden ring, while the roof sections are joined below the cupola by a rigid pinned wooden collar. The cupola also serves as a natural chimney for hot air, an important aid to ventilation for preventing hay fires and spoilage. Atop the cupola is a flat sheet metal weather vane, a primitive utilitarian form of pennon or notched banner tail arrow vane, placed high to help the farmer judge changing winds and anticipate weather conditions that could affect the cutting, stacking, and storing of hay.