Indiana - Area of significance: Architecture
| North Washington Street Historic District |
| Northwood Historic District |
| Norton, C. S., Mansion |
| Nowels, David & Sarah, House |
| Oakdale Historic District |
| Oakdale School |
| Oak Hill Cemetery |
| Oaklandon Historic District |
| O'Donnell Building |
| O'Hair, James Edington Montgomery, House |
| Ohio Boulevard-Demming Park Historic District |
| Old Bittermann Building |
| Old Cathedral Complex |
| Old Clifty Church |
| Old Courthouse (Second St. Joseph County Courthouse) |
| Old Crescent, The |
| Old East Historic District |
| Oldenburg Historic District |
| Olde Store (John O'Ferrell Store) |
| Old Fellwock Auto Company |
| Oldfields |
| Old Frankfort Stone High School |
| Old Greencastle Historic District |
| Old Hoosier Theatre |
| Old Jeffersonville Historic District |
| Old Newburgh Presbyterian Church |
| Old Northside Historic District |
| Old Plat Historic District |
| Old Richmond Historic District |
| Old Silk Stocking Historic District |
| Old State Bank |
| Old Timbers |
| Old Vanderburgh County Courthouse |
| Old Warrick County Jail |
| Old West End Historic District |
| Oliver, Joseph D., House |
| O'Neall, Abijah II, House |
| Opel, John, House |
| Orange County Courthouse |
| Oriental Lodge No. 500 |
| Original Newburgh Historic District |
| Orleans Historic District |
| Orr Iron Company |
| Orr, Robert, Polygonal Barn |
| Orr, William, House |
| Osgood, Dr. H. G., House |
| Otis Park and Golf Course |
| Our Savior Lutheran Church |
| Owen County Courthouse |
| Oxford |
| Oxford Community Mausoleum |
| Palace Lodge |
| Palace Theater |
| Palais Royale Building |
| Paoli Historic District |
| Paramount Theater Building |
| Parker, Oren F. and Adelia, House |
| Park Mary Historic District |
| Parkview Home of Clinton County |
| Parson and Scoville Building |
| Patterson Place Historic District |
| Peabody Memorial Tower |
| Peacock Apartments |
| Pearl Steam Laundry |
| Pearson, Lora B., School |
| Pearson Terrace |
| Peirce, Oliver Webster Jr., and Catherine House |
| Pendleton Historic District |
| Pennslyvania Railroad Station |
| Pennsylvania |
| Perrin Historic District |
| Peru Courthouse Square Historic District |
| Peru High School Historic District |
| Peru Westside Historic District |
| Peters, Henry, House |
| Peters, John Claus, House |
| Pierce, James, Jr., House |
| Pierceton Historic District |
| Pierson-Griffiths House |
| Pike County Courthouse |
| Pike Inn, Old |
| Pinehurst Hall |
| Pinhook Methodist Church and Cemetery |
| Place, Willard B., House |
| Plainfield Historic District |
| Plaza |
| Pleak, Strauther, Round Barn |
| Pleasant Hill Church |
| Pleasanton in Irvington Historic District |
| Pleasant Ridge Historic District |
| Pletcher, Richard and Susan, House |
| Plum Prairie Residential Historic District |
| Plymouth Downtown Historic District |
| Plymouth Fire Station |
| Plymouth Northside Historic District |
| Plymouth Southside Historic District |
| Point Historic District |
| Pokagon State Park |
| Poland Presbyterian Church and Cemetery |
| Polk Street Concrete Cottage Historic District |
Data from United States Park Service and Wikidata
