All - Constructed - 1880–1889
| Old Main, Nebraska Wesleyan University |
| Old Morris County Courthouse |
| Old Orlando Railroad Depot |
| Old Post Office Building and Customhouse |
| Old Santa Fe Railroad Depot |
| Old Sedgwick County Courthouse |
| Old Taylor Distillery |
| Oldtown Covered Bridge |
| Old Union Depot |
| Olive Branch High School |
| Olney Carnegie Library |
| Olsen House |
| Olsen, Lars and Christina, House |
| Omer Christian Church and Cemetery |
| Oneida Stake Academy |
| ONOKO (Bulk Freight Steamer) Shipwreck |
| Ontonagon County Courthouse |
| Oregon Railway and Navigation Company Bridge |
| O'Rourke, Capt. John, House |
| Orris, Adam, House |
| Osborne Apartments |
| Osceola County Courthouse |
| Oshkosh Grand Opera House |
| Osmund Osmundson House |
| O Street Market |
| Oswego West Pierhead Lighthouse |
| Otis-Wyman House |
| Our Lady of Loretto Roman Catholic Church and Cemetery |
| Oviatt House |
| Pacific Coast Company House No. 75 |
| Packer Memorial Chapel |
| Palmer-Ferril House |
| Parker County Courthouse |
| Parker House |
| Parkhurst Memorial Presbyterian Church |
| Parque de Bombas de Ponce |
| Passage Island Light Station |
| Patten, Jacob H., House |
| Paulding County Courthouse |
| Pauteon Otero-Martinez |
| Payne, Theodore F., House |
| Peabody City Park |
| Peabody, Francis Stuyvesant, House |
| Peaceful Valley Ranch |
| Pease, Robert L., House |
| Pennsylvania Railroad Station at Wayne |
| Pension Building |
| Perrault, George O., House |
| Perryman Ranch Headquarters |
| Persinger House |
| Peters, Charles, Sr., House |
| Peterson, Mathias, Homestead |
| Pettit Cleaners Building |
| Pflueger General Merchandise Store and Annex Saloon |
| Phillips, R. O., House |
| Phipps, William H., House |
| Pickering, I. O., House |
| Pickler, Maj. John A., Homestead |
| Pierce, John M., House |
| Pilgrim Congregational Church |
| Pioneer and Endicott Buildings |
| Pioneer Hall |
| Pioneer Hall, Linfield College |
| Pioneer State Bank No. 36 |
| Piper, Albert S., Homestead Claim Shanty |
| Pipe School |
| Plane, Robert R., and Julia L., House |
| Plum Grove Primitive Methodist Church |
| Poehler, August F., House |
| Point Barrow Refuge Station |
| Point Robinson Light Station |
| Point Sur Light Station |
| Poncha Springs Schoolhouse |
| Poplar Grove Plantation House |
| Porter Hollow Embankment and Culvert |
| Port Gibson Oil Works Mill Building |
| Port Sanilac Light Station |
| Pottawattamie County Sub Courthouse |
| Potters National Bank |
| Pott's Ford Bridge |
| Poughkeepsie Railroad Bridge |
| Pratt, A. W., House |
| Pratt Institute Historic District |
| Prescott Estate |
| Presidio County Courthouse |
| Probasco Fountain |
| Provo Downtown Historic District |
| Provo Tabernacle |
| Pruyn, Joel M., Block |
| Public School 71K |
| Purdy, Eliphalet W. and Catherine E. Jaquish, House |
| Putman, Walter S., House |
| Putnam Memorial State Park |
| Queen's Laundry Bath House |
| Quinn, A. V., House |
| Raburn-Casteel House |
| Raleigh Water Tower |
| Raleigh Water Works and E.B. Bain Water Treatment Plant |
| Raritan Bridge |
| Rawson, Warren, House |
Data from United States Park Service and Wikidata
