Wisconsin - Area of significance: Architecture
| Nishan, Freda Meyers, Memorial Chapel |
| No. 4 Engine House |
| North 47th Street Bungalow Historic District |
| North Broadway Street Historic District |
| Northern Block |
| North First Street Historic District |
| North Grant Boulevard Historic District |
| North Hall-River Falls State Normal School |
| North Main Street Bungalow Historic District |
| North Main Street Historic District |
| North Main Street Historic District |
| North Main Street Historic District |
| North Michigan Street-North Superior Street Historic District |
| North Milwaukee High School |
| North Point North Historic District |
| North Point South Historic District |
| North Point Water Tower |
| North Sherman Boulevard Historic District |
| Northside Historic District of Cream Brick Workers' Cottages |
| North Third Street Historic District |
| North Washington Street Historic District |
| Northwestern Branch, National Home for Disabled Volunteer Soldiers Historic District |
| Northwest Side Historic District |
| Norton, Pearl C., House |
| Norwegian Evangelic Lutheran Church and Cemetery |
| Notre Dame Church and Goldsmith Memorial Chapel |
| Nye, Clark, House |
| Oakland-Dousman Historic District |
| Oatman Filling Station |
| O'Brien-Peuschel Farmstead |
| Oconomowoc City Hall |
| Oconomowoc Depot |
| Oconto County Courthouse |
| Oconto Main Post Office |
| Octagon House |
| Octagon House |
| Oehler Mill Complex |
| Okauchee House |
| Old Ashland Post Office |
| Old Bayfield County Courthouse |
| Old Executive Mansion |
| Old Fourth Ward Historic District |
| Old Hospital |
| Old Indian Agency House |
| Old Iron County Courthouse |
| Old Main Street Historic District |
| Old Ozaukee County Courthouse |
| Old Plover Methodist Church |
| Old Rock School |
| Old Rock School |
| Old Spring Tavern |
| Old St. Mary's Church |
| Old U.S. Forest Products Laboratory |
| Old Waukesha County Courthouse |
| Old World Third Street Historic District |
| Olfson, Peter and Jessie, House |
| Oliver, Joseph B., House |
| Oliver, Owen and Margaret, House |
| Omro Downtown Historic District |
| Omro High School, Annex and Webster Manual Training School |
| Omro Village Hall and Engine House |
| Oneida County Courthouse |
| Oneida Street Station |
| Orchard Street Historic District |
| Oregon High School |
| Oregon Masonic Lodge |
| Oregon Water Tower and Pump House |
| Orfordville Depot |
| Oriental Theatre |
| Orpheum Theater |
| Orth, Phillip, Boathouse |
| Orton Park Historic District |
| Orville Beach Memorial Manual Training School |
| Osceola Commercial Historic District |
| Oshkosh State Normal School Historic District |
| Ottawa House |
| Ott, John George, House |
| Ott, Will, House |
| Our Lady of Loretto Roman Catholic Church and Cemetery |
| Our Lady of Sorrows Chapel |
| Oviatt House |
| Owen, Ray S. and Theo P., House |
| Owen, William J., Store |
| Pabst Brewery Saloon |
| Pabst Brewing Company Complex |
| Pabst, Frederick and Maria, House |
| Pabst, Gustave, Estate |
| Pabst Theater |
| Paepke, Henry, House |
| Paine Art Center and Arboretum |
| Paine Lumber Company Historic District |
| Painesville Chapel |
| Palmer Brother's Octagons |
| Palm Tree Road Bridge |
| Palo, John and Justina, Homestead |
| Pangborn, J. L., House |
| Pardeeville Presbyterian Church |
| Parker, Dwight T., Public Library |
| Park Falls Post Office |
| Park Street Historic District |
Data from United States Park Service and Wikidata
