Ohio - Criteria: A (event)
| Central High School |
| Central Ohio Lunatic Asylum |
| Central Tower Building |
| Cermak Building |
| Chalfant Church |
| Chandler, Matthew, House |
| Chaney, O. P., Grain Elevator |
| Chapman, John A., House |
| Chardon Courthouse Square District |
| Cherry Valley Coke Ovens |
| Chesapeake High School |
| Chester Town Hall |
| Chester Township District School No. 2 |
| Chesterville Methodist Church |
| Chickasaw School and Rectory |
| Childs, Alpha Charles, House |
| Christ Church At The Quarry |
| Christ Episcopal Church |
| Christ Episcopal Church |
| Christman Covered Bridge |
| Christman, Daniel, Homestead |
| Cincinnati and Suburban Telephone Company Building |
| Cincinnati and Whitewater Canal Tunnel |
| Cincinnati East Manufacturing and Warehouse District |
| Cincinnati Enquirer Building |
| Cincinnati Music Hall |
| Cincinnati Street Gas Lamps |
| Cincinnati Tennis Club |
| Cincinnati Union Terminal |
| Cincinnati Zoo Historic Structures |
| Circleville High School |
| City Hall |
| City Hall Annex |
| City Mills Building |
| City National Bank Building |
| City Savings Bank & Trust Company |
| Clague House |
| Clark, Dr., House |
| Claysville School |
| Clearview Golf Club |
| Clemens, James and Sophia, Farmstead |
| Cleveland And Pittsburgh Railroad Bridge |
| Cleveland Club |
| Cleveland Dental Manufacturing Company Building |
| Cleveland East Pierhead Light |
| Cleveland Home For Aged Colored People |
| Cleveland Hotel, The |
| Cleveland Masonic Temple |
| Cleveland Municipal Stadium |
| Cleveland Packard Building |
| Cleveland Warehouse District |
| Cleveland West Pierhead Light |
| Clifton Avenue Historic District |
| C. N. & I. Department Power House |
| Coal Run Historic District |
| Coffman, Fletcher, House |
| Cofta, Albert, Farmstead |
| Coldwater Catholic Church Complex |
| Coliseum |
| College Hall, Wilmington College |
| College Hill Town Hall |
| College of Wooster |
| Columbia Baptist Cemetery |
| Columbiana County Infirmary |
| Columbia Town Hall |
| Columbus Gallery of Fine Arts |
| Columbus Grove Municipal Pool |
| Columbus, Hocking Valley and Toledo Railway Depot |
| Columbus Near East Side District |
| Commodore Hotel, The |
| Commodore Perry Hotel |
| Concord Hicksite Friends Meeting House |
| Congregational Church Of Austinburg |
| Congregational Church of Christ |
| Conneaut Harbor West Breakwater Light |
| Conneaut Light Station Keeper's Dwelling |
| Connecticut Land Company Office |
| Cook Building |
| Cook, John, Farm |
| Coonrad, Jonas, House |
| Corwin Council House and Jail |
| Courthouse Center |
| Covenant First Presbyterian Church |
| Covington Historic Government Building |
| Cranz, Edward, Farm |
| Cranz, William and Eugene, Farm |
| Crawfis Institute |
| Crist Tavern Annex-Millworkers Boarding House |
| Crittenden Farm |
| Crosley Building |
| Crumrine, John, Farm |
| Crystal Lake Stock Farm |
| Curtiss, Marcus, Inn |
| Curtis, William D., House |
| Cuvier Press Club |
| Danford, Samuel, Farm, Church and Cemetery |
| Davis, Anson, House |
| Dayton Arcade |
| Dayton-Campbell Historic District |
| Dayton Canoe Club |
Data from United States Park Service and Wikidata
