Ohio - Area of significance: Architecture
| Cargo Warehouse |
| Carkhuff, Stacy G., House |
| Carlin, Patrick, House |
| Carnegie Library |
| Carnegie Library and Henry St. Clair Memorial Hall |
| Carnegie Library of Steubenville |
| Carnegie Library Otterbein University |
| Carnegie Public Library |
| Carpenter, Wallace W., House |
| Carroll County Courthouse |
| Carroll Township Hall |
| Carty, J.-R. J. Tussing House |
| Cary, G.W., House |
| Cary, Hiram W., House |
| Cascade Locks Historic District |
| Case-Barlow Farm |
| Casement House |
| Cassella Catholic Church and Rectory |
| Cassell, Henry, House |
| Casstown Lutheran Stone Church |
| Castalia Trout Club |
| Casterton House |
| Castle Block |
| Cawood, Richard L., Residence |
| Caxton Building |
| Cedar Glen Apartments |
| Cedar Hill Cemetery Buildings |
| Cedarville Opera House |
| Celina Main Street Commercial Historic District |
| Center Inn |
| Center Street Historic District |
| Centerville Historic District |
| Central Assurance Company |
| Central Avenue Historic District |
| Central Avenue Historic District |
| Central Branch, National Home for Disabled Volunteer Soldiers |
| Central Building of the Columbus Young Men's Christian Association |
| Central College Presbyterian Church |
| Central High School |
| Central High School |
| Central Hotel, Hackedorn and Zimmerman Building |
| Central Ohio Lunatic Asylum |
| Central Public School |
| Central School |
| Central Tower Building |
| Central United Methodist Church |
| Central YMCA |
| Central YMCA |
| Century Block |
| Chagrin Falls East Side Historic District |
| Chagrin Falls Township Hall |
| Chagrin Falls Triangle Park Commercial District |
| Chagrin Falls West Side District |
| Chalfant Church |
| Champion Coated Paper Company |
| Chandler, Matthew, House |
| Chaney, O. P., Grain Elevator |
| Chapman-Hutchinson House |
| Chapman, John A., House |
| Chardon Courthouse Square District |
| Chardon Post Office Building |
| Cheese-vat Factory |
| 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 Business District |
| Chillicothe's Old Residential District |
| Chillicothe Veterans Administration Hospital |
| Chillicothe Water And Power Company Pumping Station |
| Christ Church At The Quarry |
| Christ Episcopal Church |
| Christ Episcopal Church |
| Christman, Nicholas, House |
| Church, John, Company Building |
| Church Of Our Savior |
| Cincinnati and Suburban Telephone Company Building |
| Cincinnati City Hall |
| Cincinnati East Manufacturing and Warehouse District |
| Cincinnati Enquirer Building |
| Cincinnati Gymnasium and Athletic Club |
| Cincinnati Hebrew Day School |
| Cincinnati Music Hall |
| Cincinnati Observatory Building |
| Cincinnati Union Terminal |
| Cincinnati Work House and Hospital |
| Circleville High School |
| Circleville Historic District |
| Cisler Terrace |
| 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 |
Data from United States Park Service and Wikidata
