Ontonagon County Michigan has 7 places on the National Register of Historic Places including 1 place of Statewide significance. Significant places include Ontonagon County Courthouse, Bergland Administrative Site, Ontonagon Harbor Piers Historic District, Ontonagon Lighthouse.
Some of the country's most noteable architects helped create the Ontonagon County places including Gilbert & Denar Charlton, F.W. Chittenden and US Army Corps of Engineers. Prominent architectural styles found in Ontonagon Country are Colonial Revival.