Ohio - Criteria: C (architecture/engineering)
| Pennsylvania Depot |
| Pennsylvania House |
| Pennsylvania Railway Station |
| Peoples Bank Company Building |
| People's Federal Savings and Loan Association |
| Perkins, Col. Simon, Mansion |
| Perrill-Goodman Farm House |
| Perry County Courthouse and Jail |
| Perry-Payne Building |
| Perrysburg Water Maintenance Building |
| Pershing, Christian, Barn |
| Peters Cartridge Company |
| Peters, Stevenson, House |
| Pfarr Log House |
| Pfleger Family Houses |
| Pfleiderer Center for Religion and the Humanities |
| Philothea Catholic Church and Priest House |
| Phoenix Block |
| Phoenix Building/Cincinnati Club |
| Phoenix Club |
| Piatt, Abram S., House and Piatt, Donn S., House |
| Pickands, Jay M., House |
| Pilgrim Congregational Church |
| Pilgrim Presbyterian Church |
| Pinecroft |
| Pine Meer |
| Pinney, Dr. Eli, House |
| Piqua-Caldwell Historic District |
| Piqua High School |
| Piqua Historical Area State Memorial |
| Pisgah Christian Church |
| Pitman, Ben, House |
| Pittsburg, Cincinnati, and St. Louis Depot |
| Pitzer, Anthony, Jr., House |
| Playhouse Square Group |
| Plaza Apartments |
| Plaza Hotel |
| Pleasant Hill |
| Pleasant Hill United Church of Christ |
| Pleasant Ridge United Methodist Church and Cemetery |
| Plum Street Temple |
| Plymouth Greenlawn Cemetery Chapel |
| Point, Nathaniel, Farm |
| Poland Center School |
| Police Station No. 2 |
| Police Station No. 3 |
| Police Station No. 5 |
| Police Station No. 6 |
| Police Station No. 7 |
| Pollack, Isaac, House |
| Pollock, John C., House |
| Pomerene House |
| Pomeroy, Alanson, House |
| Ponn Humpback Covered Bridge |
| Port Clinton City Hall |
| Porter-Aue House |
| Porter, Orin, House |
| Portsmouth Fire Department No. 1 |
| Portsmouth Foundry and Machine Works |
| Port Washington Town Hall |
| Potters National Bank |
| Potters Savings and Loan |
| Pottorf, Henry and Mary, House and Farmstead |
| Powell, Andrew, Homestead |
| Powell, Henry, House |
| Power Building |
| Pray-Starkweather House |
| Prentiss, Frederick, House |
| Prentiss-Tulford House |
| Presbyterian Parsonage |
| President's House |
| Pretzinger, Rudolph, House |
| Price Corners |
| Price, Jonathan, House |
| Principal's Cottage |
| Pringle-Patric House |
| Probasco Fountain |
| Probasco, Henry, House |
| Procter and Collier-Beau Brummell Building |
| Promont |
| Prospect Hill Historic District |
| Prospect Place |
| Pugh-Kittle House |
| Pugh's Mill Covered Bridge |
| Purcell, Robert A. and Elizabeth H., House |
| Purdum-Tracy House |
| Putman, Walter S., House |
| Putnam County Courthouse |
| Putnam Historic District |
| Putnam, Rufus, House |
| Pythian Castle |
| Pythian Temple and James Pythian Theater |
| Race Street Historic District |
| Rae, Capt., House |
| Raemelton Farm Historic District |
| Rager, John, Farmhouse |
| Ragersville School |
| Rankin Building |
| Ranney, Luther B., Farm |
| Ransley Apartment Building |
Data from United States Park Service and Wikidata
