| Citreous Steel | Nappanee | IN |
| City & County Building | Fort Wayne | IN |
| City & County Building | Jeffersonville | IN |
| City County Court House Building | Fort Wayne | IN |
| City County Jail | Columbus | IN |
| City Electric Lighting | Vincennes | IN |
| City Hospital | Indianapolis | IN |
| City Maintenance Garage | Indianapolis | IN |
| City Roofing | Elkhart | IN |
| City Service Oil | East Chicago | IN |
| City Water Department | Mishawaka | IN |
| City Water Works | Lafayette | IN |
| Clarence Figel Construction | Fort Wayne | IN |
| Clay City Hospital | Brazil | IN |
| Cleaner-Brooks | La Porte | IN |
| Cleveland Township School | South Whitley | IN |
| Clifty Creek Power Plant | Madison | IN |
| Clinton Electric Light & Power | Clinton | IN |
| Clinton Ice | Clinton | IN |
| Close Insulation | Fort Wayne | IN |
| C. Miller & Sons | Fort Wayne | IN |
| Coca Cola | Greencastle | IN |
| Coil Engineering & Manufacturing | Roanoke | IN |
| Coke & Coal Chemical Division | Gary | IN |
| Coldwell & Company | Terre Haute | IN |
| Colgate Palmolive | Jeffersonville | IN |
| Columbia Elem School | Bluffton | IN |
| Columbia Enamel & Stamping | Terre Haute | IN |
| Columbia Improvement | Terre Haute | IN |
| Columbian Enameling & Stamping | Terre Haute | IN |
| Columbia Records Manufacturing Facility | Terre Haute | IN |
| Columbia Woolen Mills | Columbia | IN |
| Columbus Food | Shelbyville | IN |
| Columbus High School | Columbus | IN |
| Combustion Engineering | East Chicago | IN |
| Commercial Distillery | Terre Haute | IN |
| Commercial Floor Covering | Indianapolis | IN |
| Commercial & Industrial Insulations | Indianapolis | IN |
| Commercial Insulation & Acoustic | Fort Wayne | IN |
| Commercial Solvents | Terre Haute | IN |
| Commonwealth Edison | Hammond | IN |
| Community Hospital Of Indianapolis | Indianapolis | IN |
| Como Chemical | Kokomo | IN |
| Components | East Chicago | IN |
| Connersville Blower | Connersville | IN |
| Consolidated Railway | Huntington | IN |
| Consolidated Railway | Elkhart | IN |
| Consumer Electronics Division | Indianapolis | IN |
| Container Company Of America | Anderson | IN |
| Container Company Of America | Wabash | IN |
