Ohio - Criteria: C (architecture/engineering)
| Ratterman, Bernard, House |
| Rattermann, Heinrich A., House |
| Rauh, Frederick and Harriet, House |
| Rawlings-Brownell House |
| Rawson House |
| Rayen School |
| Raymond, Frank Mason, House |
| Raymond, Liberty G., Tavern and Barn |
| Reakirt Building |
| Reamer Barn |
| Reaves, John, House |
| Reber, Valentine, House |
| Red Brick Tavern |
| Redington Block |
| Redlands |
| Red Oak Presbyterian Church |
| Red Oak-Sherman, William C., House |
| Reed, C. A., House |
| Reed Covered Bridge |
| Reed, Henry, Jr., House |
| Reed, James, House |
| Reed, Joseph G., Company |
| Reeves, Jeremiah, House and Carriage House |
| Reid, Whitelaw, House |
| Renick Farm |
| Renick House, Paint Hill |
| Renkert, Harry S., House |
| Renner, George J., Jr., House |
| Rentschler House |
| Renz Block |
| Resor, William, House |
| Retszch, W. C., House |
| Reynolds, John R., House |
| Rhoads, Peter F., House |
| Rhodes and Watters Apartment Buildings, The |
| Richard, John, Residence |
| Rich, Charles B., House |
| Richey, James, Farmhouse |
| Richland Trust Building |
| Richman Brothers Company, The |
| Riddle Block |
| Riddle Block #11 |
| Riddle Block #9 |
| Riddle-Friend House |
| Rider, Adam, House |
| Ridgewood Historic District |
| Riley, Calvin E., House |
| Rinard Covered Bridge |
| Rinderknecht, Christian H., House |
| Rinehart, Hugh T., House |
| Ripley House |
| Ritter, William, House |
| Riverside Cemetery Building |
| Riverside Cemetery Chapel |
| Riverside Chapel |
| Riverview |
| Riverview Apartments |
| Roas-Ilhardt Farm and Winery |
| Robb, L. B., Drugstore |
| Roberts Covered Bridge |
| Robeson, Dr. Donovan, House |
| Robinson, Byron W., House |
| Robinson, Edmund, House |
| Robinson-Pavey House |
| Rock Creek School |
| Rockefeller Building |
| Rockefeller Park and Cleveland Cultural Gardens Historic District |
| Rockefeller Park Bridges |
| Rock Hill Presbyterian Church |
| Rock Mill |
| Rock Mill Covered Bridge |
| Rodrick Bridge |
| Rogers House |
| Rohr, David, Mansion And Carriage House |
| Rookwood Pottery |
| Root, A. I. And E. R., Homestead |
| Root and McBride-Bradley Building |
| Root Covered Bridge |
| Root, Joseph, House |
| Root, William H., House |
| Ropes, Nathaniel, Building |
| Roscoe Village |
| Rose, Capt. Levi, House |
| Rossville Historic District |
| Roudebush Farm |
| Round Barn |
| Round Barn |
| Round Barn |
| Round Barn |
| Round Barn |
| Round Hill |
| Royalton House |
| Rubicon Farm |
| Ruggles, Charles, House |
| Russell, Charles B., House |
| Russell, Mark, House |
| Sachs and Pruden Ale Company Building |
| Sacred Heart Academy |
| Sacred Heart Church |
| Sacred Heart of Jesus Churches |
Data from United States Park Service and Wikidata
