Ohio - Significance region: Local
| Conner, Alexander, House |
| Conover Building |
| Conrad Mound Archeological Site |
| Consolidated Fruit Auction Company Building |
| Converse-Mertz Apartments |
| Convoy Opera House-City Hall-Firehouse Building |
| Cook Building |
| Cooke, Eleutheros, House |
| Cooke, Eleutheros, House |
| Cooke-Robertson House |
| Cook, George E., House |
| Cook, J.M., House |
| Cook, John, Farm |
| Cook, Zimri, House |
| Coon Hunters Mound |
| Coonrad, Jonas, House |
| Cooper, Katherine, House |
| Cooper, Samuel, Farmhouse |
| Copley Depot |
| Copley Township Cemetery Receiving Vault |
| Corbusier, John William Creswell, House |
| Corlett Building |
| Corwin Council House and Jail |
| Cory, Ambrose, House |
| Coshocton Main Street Historic District |
| Cote Bonneville |
| Cottage Hill Farm |
| Coulby, Harry, Mansion |
| Courthouse Center |
| Courtland Flats |
| Courtland, The |
| Court Street Firehouse |
| Covenant First Presbyterian Church |
| Covington Historic Government Building |
| Cowan Creek Circular Enclosure |
| Cox, George B., House |
| Cox, Jacob D., House |
| Cozad, Justus L., House |
| Crabill, David, House |
| Craft Master Building |
| Crafts William H., House |
| Crandall Park-Fifth Avenue Historic District |
| Crane, Jonathan, Farm |
| Cranz, Edward, Farm |
| Cranz, William and Eugene, Farm |
| Crawfis Institute |
| Crawford, Col. William, Capture Site |
| Crawford-Tilden Apartments |
| Crescent Hill |
| Crescent, The |
| Crestline City Hall |
| Crist Tavern Annex-Millworkers Boarding House |
| Crittenden Farm |
| Croco House |
| Cronenwett, Georg, House |
| Crosley Building |
| Crumrine, John, Farm |
| Crumrine, Michael, Farm |
| Crystal Lake Stock Farm |
| Culbertson, Robert, House |
| Cummings, Wilson S., House |
| Cummins, David, Octagon House |
| Cummins School |
| Cunningham-Maier House |
| Curry Farm Historic District |
| Curtiss, Marcus, Inn |
| Curtis, Walter, House |
| Curtis, William D., House |
| Cuvier Press Club |
| Cuyahoga Falls Downtown Historic District |
| Dall, Andrew, Jr. and James, Houses |
| Damascus Grade School |
| Damon, George, House |
| Danalds, Samuel, House |
| Dana, Marcus, House |
| Danford, Samuel, Farm, Church and Cemetery |
| Datz, Walter, House |
| Davey, John, House |
| Davidson, Tyler, Fountain |
| David's Reformed Church |
| Davis, Alexander, Cabin |
| Davis, Alexander, House |
| Davis and Dague Grocery Store, Old |
| Davis, Anson, House |
| Davis, Anson, Springhouse |
| Davis, James, Barn |
| Davis, James, Farm |
| Davis Mill |
| Davis, Samuel Henry, House |
| Davis, Samuel, House |
| Davis Works |
| Dawes Arboretum, The |
| Day, Erastus, House |
| Dayton-Campbell Historic District |
| Dayton Canoe Club |
| Dayton Country Club |
| Dayton Daily News Building |
| Dayton Fire Department Station No. 16 |
| Dayton Fire Station No. 14 |
| Dayton, James, House |
Data from United States Park Service and Wikidata
