The last round barn built in Indiana was in 1936. Land grant colleges including Purdue University advocated round barns as economical in the early 1900's. The University of Illinois published a booklet, The Economy of the Round Barn, in 1910. But they advised putting a silo in the middle to help support the roof. Fulton County's round barns do not have silos, but have unsupported roofs.
Round barns are more economical in several ways.
The capacity of a circle is larger than that of a rectangle with the same amount of siding. Having the livestock all face the center saved the farmer steps when feeding. Several are disappearing every year. They cost too much to repair, and farmers cannot afford to pay taxes on them for storage because the big modern farm tractors and machinery won't fit through the doors. The neglected barns are succumbing to wind, weather and fire and are being torn down.