Ohio - Significance region: Local
| Christ Episcopal Church |
| Christman, Daniel, Homestead |
| Christman, Nicholas, House |
| Christy, Howard Chandler, Art Studio |
| Church, John, Company Building |
| Cincinnati and Suburban Telephone Company Building |
| Cincinnati City Hall |
| Cincinnati East Manufacturing and Warehouse District |
| Cincinnati Enquirer Building |
| Cincinnati Gymnasium and Athletic Club |
| Cincinnati, Hamilton, and Dayton Railroad Station |
| Cincinnati Hebrew Day School |
| Circleville High School |
| Circleville Historic District |
| Cisler Terrace |
| City Hall |
| City Hall and Opera House |
| City Mills Building |
| City National Bank Building |
| City Savings Bank & Trust Company |
| Clague House |
| Clark, Ansel, House |
| Clarke Farm Site |
| Clark, Jared, House |
| Clark, Whitney, House |
| Clauder's Pharmacy |
| Claysville School |
| Clearview Golf Club |
| Clemens, James and Sophia, Farmstead |
| Clement, George S., House |
| Clemmons, W.C., Mound |
| Clemons, Alexander, House |
| Clester, Joseph, House |
| Cleveland Centre Historic District |
| Cleveland Club |
| Cleveland, Columbus, Cincinnati & Indianapolis Railroad Depot |
| Cleveland Dental Manufacturing Company Building |
| Cleveland Discount Building |
| Cleveland East Pierhead Light |
| Cleveland Grays Armory |
| Cleveland Home For Aged Colored People |
| Cleveland Hotel, The |
| Cleveland Jewish Center-Cory United Methodist Church |
| Cleveland Masonic Temple |
| Cleveland Municipal Stadium |
| Cleveland Packard Building |
| Cleveland State University-University Tower |
| Cleveland Trust Company |
| Cleveland Worsted Mills Company |
| Cleveland Worsted Mills Redfern Mill |
| Clifton Methodist Episcopal Church |
| Clifton Park Lakefront District |
| Clifton Park South Historic District |
| Clinton Apartments |
| Clinton Ohio and Erie Canal Historic District-Clinton Lock 2 and 3-Clinton Upper (Lock 2) and Clinton Lower (Lock 3) |
| Clossman Hardware Store |
| Clough Creek and Sand Ridge Archeological District |
| Clutts House |
| Coal Run Historic District |
| Cochran Farm |
| Coe Mound |
| Coe, Truman and Sylvia Bull, House |
| Coffman, Fletcher, House |
| Cofta, Albert, Farmstead |
| Coliseum |
| College Hill Historic District |
| College Hill Town Hall |
| College of Wooster |
| Colonial and Euclid Arcades |
| Colonial, The |
| Colony Burying Ground, Old |
| Columbia Baptist Cemetery |
| Columbia Baptist Church |
| Columbia Building |
| Columbiana County Infirmary |
| Columbia Town Hall |
| Columbus Avenue Historic District |
| Columbus Carriage Manufacturing Co. - Seagrave Co. Buildings |
| Columbus Center |
| Columbus Country Club Mound |
| Columbus Gallery of Fine Arts |
| Columbus Grove Municipal Pool |
| Columbus, Hocking Valley and Toledo Railway Depot |
| Columbus Street Historic District |
| Columbus Transfer Company Warehouse |
| Commercial Banking & Trust Co. |
| Commercial Building |
| Commercial Building |
| Commercial Street Historic District |
| Commodore Apartment Building |
| Commodore Hotel, The |
| Commodore Perry Hotel |
| 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 |
| Conneaut Works |
| Connecticut Land Company Office |
Data from United States Park Service and Wikidata
