| Canal Street Garage | Cincinnati | OH |
| Candle Lite Homes | Columbus | OH |
| Canton Casting | Canton | OH |
| Canton Defense Plant | Canton | OH |
| Canton Die | Canton | OH |
| Canton Drop Forge Plant | Massillon | OH |
| Canton Drop Forge Plant | Canton | OH |
| Canton Electric | Canton | OH |
| Canton Forge & Axle | Canton | OH |
| Canton Harrison S. M. | Louisville | OH |
| Canton Hughes Pump | Canton | OH |
| Canton Laundry & Cleaning | Canton | OH |
| Canton Light, Heat & Power | Canton | OH |
| Canton Malleable Iron | Canton | OH |
| Canton Naval Ordnance Plant | Canton | OH |
| Canton Saw | Canton | OH |
| Canton Screen Plant | Canton | OH |
| Canton Sewage | Canton | OH |
| Canton South High School | Canton | OH |
| Canton Steel Foundry | Canton | OH |
| Canton Storage | Canton | OH |
| Canton Water Pollution Control Center | Canton | OH |
| Capital City Products | Columbus | OH |
| Capitol Savings & Trust | Columbus | OH |
| Carbon Black | Belpre | OH |
| Carbo Tool & Die | Fremont | OH |
| Cardinal Operating | Brilliant | OH |
| Cardinal Power Plant | Brilliant | OH |
| Carew Building | Cincinnati | OH |
| Carew Tower Building | Cincinnati | OH |
| Cargill | Dayton | OH |
| Carlisle Chemical Works | Reading | OH |
| Carl Meyer | Rocky River | OH |
| Carlson Fabricating & Welding | Lorain | OH |
| Carnahan Tin Plate & Sheet | Canton | OH |
| Carnation Milk Products | Hillsboro | OH |
| Carnation Milk Products | Coshocton | OH |
| Carnegie Steel | Cleveland | OH |
| Carnegie Steel | Canton | OH |
| Carnegie Steel | Mingo Junction | OH |
| Carnegie Steel | McDonald | OH |
| Carnegie Steel | Columbus | OH |
| Carnegie Steel | Youngstown | OH |
| Carnegie Steel | Fairport Harbor | OH |
| Carnegie Steel | Bellaire | OH |
| Carney Paper | Maumee | OH |
| Carrier | Akron | OH |
| Carroll Foundry & Machine Works | Bucyrus | OH |
| Carrousel Shopping Center | Cincinnati | OH |
| Carter Jones Lumber | Akron | OH |
