High Quality Content by WIKIPEDIA articles! A round barn is a historic barn design that could be octagonal, polygonal, or circular in plan. Though round barns were not as popular as some other barn designs, their unique shape makes them noticeable. The years from 1880–1920 represent the height of round barn construction. Round barn construction in the United States can be divided into two distinct eras. The first, the octagonal era, spanned from 1850–1900. The second era, known as the true circular era, spanned from 1889–1936. The overlap meant that round barns of both types, polygonal and circular, were built during the period that round barns were popular in the United States. Numerous round barns in the United States are listed on the National Register of Historic Places.