Oliver Green Traphagen (3 September 1854 – 21 October 1932)[1] was an American architect who designed many notable buildings in Duluth, Minnesota, during the late 19th century and in the Territory of Hawaii during the early 20th century. Among his most famous landmarks are the Oliver G. Traphagen House in Duluth, called the Redstone,[2] and the Moana Hotel in Honolulu, both of which are on the National Register of Historic Places, as are several other buildings he designed.