Ohio - Area of significance: Architecture
| Clark, Ansel, House |
| Clark, Dr., House |
| Clark, Jared, House |
| Clark, Whitney, House |
| Clauder's Pharmacy |
| Claysville School |
| Clement, George S., House |
| Clemons, Alexander, House |
| Clester, Joseph, House |
| Cleveland And Pittsburgh Railroad Bridge |
| Cleveland Arcade |
| Cleveland Centre Historic District |
| Cleveland Club |
| Cleveland Dental Manufacturing Company Building |
| Cleveland Discount Building |
| Cleveland East Pierhead Light |
| Cleveland Grays Armory |
| Cleveland Harbor Station, U.S. Coast Guard |
| Cleveland Hotel, The |
| Cleveland Jewish Center-Cory United Methodist Church |
| Cleveland Mall |
| Cleveland Masonic Temple |
| Cleveland Municipal Stadium |
| Cleveland Packard Building |
| Cleveland Public Square |
| Cleveland State University-University Tower |
| Cleveland Trust Company |
| Cleveland Warehouse District |
| Cleveland Worsted Mills Company |
| Cleveland Worsted Mills Redfern Mill |
| Clifton Avenue Historic District |
| Clifton Methodist Episcopal Church |
| Clifton Park Lakefront District |
| Clifton Park South Historic District |
| Clinton Apartments |
| Clossman Hardware Store |
| Clutts House |
| C. N. & I. Department Power House |
| Coca-Cola Bottling Corporation |
| Cochran Farm |
| Coe, Truman and Sylvia Bull, House |
| Coffeen, Goldsmith, House |
| Coffman, Fletcher, House |
| Coldwater Catholic Church Complex |
| Cole Avenue Housing Project Historic District |
| Coliseum |
| College Hall |
| College Hall, Wilmington College |
| College Hill Historic District |
| College Hill Town Hall |
| College of Wooster |
| Colonial and Euclid Arcades |
| Colonial, The |
| Columbia Baptist Church |
| Columbia Building |
| Columbiana County Infirmary |
| Columbian House |
| Columbia Town Hall |
| Columbus Avenue Historic District |
| Columbus Center |
| Columbus Gallery of Fine Arts |
| Columbus Grove Municipal Pool |
| Columbus, Hocking Valley and Toledo Railway Depot |
| Columbus Near East Side District |
| Columbus Savings and Trust Building |
| Columbus Street Historic District |
| Columbus Transfer Company Warehouse |
| Commercial Banking & Trust Co. |
| Commercial Building |
| Commercial Building |
| Commercial Street Historic District |
| 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 |
| Cooley Farms |
| 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 |
| Corlett Building |
Data from United States Park Service and Wikidata
