The Sinnett Octagon House built in 1855 is a historic octagonal house in Muscatine, Iowa. The two-story brick home with wrap-around porch and windowed cupola is now used as an office building. On July 18, 1974, it was added to the National Register of Historic Places. References Octagon houses in Iowa Houses completed in 1855 Houses on the National Register of Historic Places in Iowa Houses in Muscatine County, Iowa National Register of Historic Places in Muscatine County, Iowa Buildings and structures in Muscatine, Iowa