This site will soon be connected to a collection of resources on the mid-19th century fad for building octagonal houses, and related material. The octagon mode was popularized by Orson S. Fowler in his books and lecture tours starting in 1848.
We are also developing a U.S. and worldwide inventory of polygonal and round structures, together with photos, plans, National Register status, etc., where available; biographical material on Fowler; information on round and polygonal barns; and an extensive bibliography on the subject. Check back in a few weeks to see how it's coming along.