All - Architectural style - Italianate architecture
| Morgan, W. H., House |
| Morrison House |
| Morse and Wade Building |
| Morse-Libby Mansion |
| Morse-Scoville House |
| Moss Grove Plantation House |
| Mount Auburn Cemetery Reception House |
| Mount Holly |
| Mount Pleasant |
| Mount Pleasant House |
| Murray, George, House |
| Murray, Robert, House |
| Muskingum County Courthouse And Jail |
| Myers-Spalti Manufacturing Plant |
| Myrtle Bank |
| Naeset, Jens, House |
| National Teacher's Normal and Business College Administration Building |
| Navarro, Jose Antonio, Elementary School |
| Nenney, J. P., House |
| Netcott-Pfeiffer House |
| Nettleton-Mead House |
| Newberry College Historic District |
| Newberry, Milo Prentice, House |
| New Haven Clock Company Factory |
| Newton-Allaire House |
| Newton, George, House |
| New York Executive Mansion |
| Nichols, Capt. John P., House |
| Nichols, John H., House |
| Niewerth Building |
| Niles, Rial A., House |
| Nims, William Reuben, House |
| No. 4 Engine House |
| Noble Block |
| Noble-Seymour-Crippen House |
| Nodaway County Courthouse |
| Norton, Charles Henry and Charlotte, House |
| Norton, Gould Hyde, House |
| Noyes, Jacob, Block |
| Oakes-Wood House |
| Oaklands, The |
| Oberlin Lake Shore And Michigan Southern Station |
| O'Connor, Thomas M., House |
| Octagon House |
| Oddfellows Hall |
| Odd Fellows Hall |
| Odd Fellows Hall |
| Odd Fellows Hall |
| Ogilvie Building |
| O'Hara Waltham Dial Company |
| Ohlman-Shannon House |
| Old California City Hall and Fire Station |
| Old Engine Company No. 6 |
| Old Executive Mansion |
| Old Homestead |
| Old Logan County Courthouse |
| Old Santa Fe Railroad Depot |
| Olsen House |
| Omaha National Bank Building |
| Ormsby-Kelly House |
| O'Rourke, Capt. John, House |
| Osceola Masonic Block |
| Ott, John George, House |
| Oversen, Julius and Anine House |
| Overstreet House |
| Paddock, Augustus, House |
| Paddock, Henry I., House |
| Palace Hotel |
| Palace Theatre |
| Palmer, Albert, House |
| Palmer, Gen. Joseph B., House |
| Parker-Burnett House |
| Parker, Harrison, Sr., House |
| Patten Building |
| Patten, Jacob H., House |
| Pawtucket Congregational Church |
| Peabody Institute Library |
| Pease, Robert L., House |
| Peck Block |
| Pedrick, Marcellus, House |
| Pennington, Governor John L., House |
| Percy-Lobdell Building |
| Perrigo-Holmes House |
| Perry, Clark, House |
| Perry County Jail |
| Philbrook, Samuel D., House |
| Phillips and Trosper Buildings |
| Physicians Building |
| Pickens County Courthouse |
| Pickering, I. O., House |
| Piedmont Park Apartments |
| Pilot Point Commercial Historic District |
| Pinehill |
| Pine Tree Lumber Company Office Building |
| Pinkham, Richard, House |
| Pioneer Courthouse |
| Pioneer Hall, Linfield College |
| Pioneer Trunk Factory-C. A. Malm & Co. |
| Piper, Daniel S., House |
| Pittock Mansion |
Data from United States Park Service and Wikidata
