Ohio - Criteria: C (architecture/engineering)
| Columbus, Hocking Valley and Toledo Railway Depot |
| Columbus Near East Side District |
| Columbus Savings and Trust Building |
| Columbus Transfer Company Warehouse |
| Commercial Banking & Trust Co. |
| Commercial Building |
| Commercial Building |
| Commodore Apartment Building |
| Commodore Perry Hotel |
| Concord Hall |
| Concord Hicksite Friends Meeting House |
| Congregational Church Of Austinburg |
| Congregational Church of Christ |
| Congregational-Presbyterian Church |
| Conneaut Harbor West Breakwater Light |
| Conneaut Light Station Keeper's Dwelling |
| Connecticut Land Company Office |
| Conner, Alexander, House |
| Conover Building |
| Converse-Mertz Apartments |
| Cook Building |
| Cooke, Eleutheros, House |
| Cooke, Eleutheros, House |
| Cooke-Robertson House |
| Cook, George E., House |
| Cook, J.M., House |
| Cook, Zimri, House |
| Coonrad, Jonas, House |
| Cooper, Katherine, House |
| Cooper, Samuel, Farmhouse |
| Copley Depot |
| Copley Township Cemetery Receiving Vault |
| Coppess, Benjamin Franklin House |
| Corbusier, John William Creswell, House |
| Corning-White House |
| Corwin-Bolin House |
| Corwin Council House and Jail |
| Corwin House |
| Cory, Ambrose, House |
| Coshocton County Courthouse |
| Cote Bonneville |
| Coulby, Harry, Mansion |
| Courthouse Center |
| Courtland Flats |
| Courtland, The |
| Court Street Firehouse |
| Covenant First Presbyterian Church |
| Cox, George B., House |
| Cox, Jacob D., House |
| Cozad, Justus L., House |
| Crafts William H., House |
| Crane, Jonathan, Farm |
| Cranz, Edward, Farm |
| Cranz, William and Eugene, Farm |
| Crawfis Institute |
| Crawford-Tilden Apartments |
| Crist Tavern Annex-Millworkers Boarding House |
| Crittenden Farm |
| Croco House |
| Cronenwett, Georg, House |
| Crosley Building |
| Crossed Keys Tavern |
| Crumrine, John, Farm |
| Crystal Lake Stock Farm |
| Culbertson, Robert, House |
| Culbertson, William, House |
| Cummings, Wilson S., House |
| Cummins, David, Octagon House |
| Cummins School |
| Curtiss, Marcus, Inn |
| Curtis, Walter, House |
| Cuvier Press Club |
| Damascus Grade School |
| Damon, George, House |
| Dana, Marcus, House |
| Danford, Samuel, Farm, Church and Cemetery |
| Darke County Courthouse, Sheriff's House, And Jail |
| Davey, John, House |
| Davidson, Tyler, Fountain |
| David's Reformed Church |
| Davis and Dague Grocery Store, Old |
| Davis, Anson, House |
| Davis, Samuel, House |
| Dawes Arboretum, The |
| Dayton Arcade |
| Dayton Art Institute |
| Dayton-Campbell Historic District |
| Dayton Canoe Club |
| Dayton Daily News Building |
| Dayton Fire Department Station No. 16 |
| Dayton Fire Station No. 14 |
| Dayton, James, House |
| Dayton, James, House, II |
| Dayton Motor Car Company Historic District |
| Dayton Street Historic District |
| Dayton View Historic District |
| Dayton Women's Club |
| Dayton Young Men's Christian Association Building |
| Dean Family Farm |
| Dean Road Bridge |
Data from United States Park Service and Wikidata
