Ohio - Criteria: C (architecture/engineering)
| Central YMCA |
| Chagrin Falls Township Hall |
| Chalfant Church |
| Chambers Road Covered Bridge |
| Chandler, Matthew, House |
| Chaney, O. P., Grain Elevator |
| Chapman-Hutchinson House |
| Chapman, John A., House |
| Chardon Courthouse Square District |
| Chardon Post Office Building |
| Chesney, Dr. John, House |
| Chester Town Hall |
| Chesterville Methodist Church |
| Chestnut Ridge Farm |
| Chickasaw School and Rectory |
| Childs, Alpha Charles, House |
| Childs, Robertus W., House |
| Chillicothe Water And Power Company Pumping Station |
| Christ Church At The Quarry |
| Christ Episcopal Church |
| Christ Episcopal Church |
| Christman Covered Bridge |
| Christman, Nicholas, House |
| Church Hill Road Covered Bridge |
| Church, John, Company Building |
| Church Of Our Savior |
| Cincinnati and Suburban Telephone Company Building |
| Cincinnati and Whitewater Canal Tunnel |
| Cincinnati City Hall |
| Cincinnati East Manufacturing and Warehouse District |
| Cincinnati Enquirer Building |
| Cincinnati Gymnasium and Athletic Club |
| Cincinnati Music Hall |
| Cincinnati Observatory Building |
| Cincinnati Street Gas Lamps |
| Cincinnati Union Terminal |
| Cincinnati Work House and Hospital |
| Circleville High School |
| Circleville Historic District |
| City Hall |
| City Hall and Opera House |
| City Hall Annex |
| City Mills Building |
| City National Bank Building |
| City Savings Bank & Trust Company |
| Clague House |
| Claridon Congregational Church |
| Clark, Ansel, House |
| Clark, Dr., House |
| Clark, Jared, House |
| Clark, Whitney, House |
| Clauder's Pharmacy |
| Claysville School |
| Clearview Golf Club |
| Clement, George S., House |
| Clemons, Alexander, House |
| Clester, Joseph, House |
| Cleveland And Pittsburgh Railroad Bridge |
| Cleveland Arcade |
| 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 Mall |
| Cleveland Masonic Temple |
| Cleveland Municipal Stadium |
| Cleveland Packard Building |
| Cleveland Public Square |
| Cleveland Trust Company |
| Cleveland Warehouse District |
| Cleveland West Pierhead Light |
| Clifton Avenue Historic District |
| Clifton Methodist Episcopal Church |
| 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 |
| Coliseum |
| College Hall |
| College Hall, Wilmington College |
| 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 Gallery of Fine Arts |
| Columbus Grove Municipal Pool |
Data from United States Park Service and Wikidata
