Secrest Octagon Barn  The Secrest Octagon Barn is a historic building located near Downey in rural Johnson County, Iowa, United States. It was constructed in 1883 by master builder George Frank Longerbean for Joshua Hunt Secrest as a hay barn-horse stable. The octagonal barn measures in diameter. It features red vertical siding and a sectional bell shaped roof that is supported by hand-laminated beams. The octagon-shaped cupola has the same roof shape as the barn. It was listed on the National Register of Historic Places in 1974. According to the builder's great grandson, the builder's name is Longerbeam.