Oliver Green Traphagen 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, and the Moana Hotel in Honolulu, both of which are on the National Register of Historic Places, as are several other buildings he designed.

The Oliver G. Traphagen House, also known as Redstone, is a historic residential building in Duluth, Minnesota, United States. Built in 1892 as a duplex, it was designed and inhabited by architect Oliver G. Traphagen (1854–1932). The building was listed on the National Register of Historic Places in 1975 for its local significance in the theme of architecture. It was nominated for its association with Traphagen, recognized together with his business partner Francis W. Fitzpatrick as Duluth's leading architects of the late 19th century.