| Container Company Of America | Carthage | IN |
| Continental Can | Elkhart | IN |
| Continental Can | Fort Wayne | IN |
| Continental Ordnance | East Chicago | IN |
| Continental Roll & Steel Fory. | East Chicago | IN |
| Continental Steel | Kokomo | IN |
| Converse Packing | Converse | IN |
| Cooney Furnace | Terre Haute | IN |
| Corning | Hammond | IN |
| Corning - Bluffton Plant | Bluffton | IN |
| Countrymark Refinery | Mount Vernon | IN |
| County Line Cheese | Fort Wayne | IN |
| Coverall Rental Service | Fort Wayne | IN |
| Crane | Butler | IN |
| Crawfordsville Electric Light & Power | Crawfordsville | IN |
| Crawfordsville Heating | Crawfordsville | IN |
| Crawfordsville Wire & Nail | Crawfordsville | IN |
| Crawfordville Power Plant | Lafayette | IN |
| Crosley | Richmond | IN |
| Crothersville High School | Crothersville | IN |
| Crown Laundry | Indianapolis | IN |
| Crow's Insulation | Evansville | IN |
| Croyton & Kinney | Angola | IN |
| C.S.G. | Shelbyville | IN |
| Cudahy Packing | East Chicago | IN |
| Culley Power Plant | Newburgh | IN |
| Cummins Engine | South Bend | IN |
| Cummins Engine | Columbus | IN |
| Cummins Engine | Walesboro | IN |
| Curtis Automotive Devices | Westfield | IN |
| Curtis-Wright | Indianapolis | IN |
| Cussen Service Center | North Manchester | IN |
| C.W. Mcdaniel | Franklin | IN |
| Dairy Farmers Of America | Goshen | IN |
| Dalton Foundries | Warsaw | IN |
| Dana | Fort Wayne | IN |
| Dana | Marion | IN |
| Dana | Auburn | IN |
| Dana | Hagerstown | IN |
| Dana | Richmond | IN |
| Dana Heavy Water Plant | Dana | IN |
| Dana Power Plant | Dana | IN |
| Dasco | Elwood | IN |
| Davis Cooperage | Martinsville | IN |
| Davis Stomer | Auburn | IN |
| Dayton & Muncie Traction | Winchester | IN |
| Dean Forging | Muncie | IN |
| Dean Forging | Gary | IN |
| Decatur Castings | Decatur | IN |
| Decatur County Bank | Greensburg | IN |
