B. O. Cutter House was created in 1856.
Fred O. Miller House was created in 1914.
William O. Munsell House was created in 1902.
O. E. Rolvaag House was created in 1912.
Reed O. Smoot House was created in 1892.
Henry O. Tanner House was created in 1872.
Horace O. Moss House was created in 1831.
William O. Butler House was created in 1819.
Andrew O. Anderson House was created in 1916.
O. E. Walker House was created in 1916.
Dr. S. O. Richardson House was created in 1837.
Sen. Joseph O. Clark House was created in 1924.
Mayor Edwin O. Childs House was created in 1915.