Now owned by the American Arcfhitecural Foundation, The Octagon ranks as the oldest museum in the US dedicated to architecture and design, and one of America's best examples of Federal-period architecture. The house was built by Dr. William Thornton, the first architect of the US Capitol. The lot was triangluar, the house is six-sided and it's named after an eight-sided figure. The house was designed and built for Colonel John Tayloe and was used as the family's winter residence from 1801 until 1817, when they moved there permanently.