| Cuno Engineering | Meriden | CT |
| Curtis Street Boiler Room | New Britain | CT |
| C.W. Blakeslee & Sons | New Haven | CT |
| Danbury Bethel Street Railway | Danbury | CT |
| Danbury Hospital | Danbury | CT |
| Danbury Rubber | Danbury | CT |
| Darien High School | Darien | CT |
| Darien Town | Darien | CT |
| De Fonce Construction | Norwalk | CT |
| Delvecchia & Sons | Wallingford | CT |
| Department Of Public Works | Greenwich | CT |
| Derby Coal & Oil | Derby | CT |
| Derby Gas | Derby | CT |
| Derby Gas & Electric | Shelton | CT |
| Derby Gas & Electric | Derby | CT |
| Dexter | Windsor Locks | CT |
| Dexter Paper | Windsor Locks | CT |
| Diamond Match | Southford | CT |
| Dictaphone | Bridgeport | CT |
| Dion Ray | Bridgeport | CT |
| Dorr-Oliver | Stamford | CT |
| Dorr-Oliver | Westport | CT |
| Dow Chemical | Gales Ferry | CT |
| Dresser Valve & Instrument | Stratford | CT |
| Dumar | Stamford | CT |
| Duo Set Processing | Ellington | CT |
| DuPont | Fairfield | CT |
| Duraphene | Sterling | CT |
| Duth Ft Rousing Project | Hartford | CT |
| Eagle Pencil | Danbury | CT |
| Eagle Picher | Stratford | CT |
| Eastern Ship Building | New London | CT |
| Eastern Trucking Siding | East Hartford | CT |
| East Hartford Housing Authority | East Hartford | CT |
| East Hartford Incinerator | East Hartford | CT |
| East Hartford Public Deliveries Tank Track | East Hartford | CT |
| East Shore Sewage Plant | New Haven | CT |
| Eaton, Cole & Burnham | Bridgeport | CT |
| Ebasco Services | Bridgeport | CT |
| Eight Glen Court | Greenwich | CT |
| Electric Boat | Groton | CT |
| Electric Boat Shipyard | Groton | CT |
| Electric Storage Battery | Fairfield | CT |
| Electrolux | Old Greenwich | CT |
| Elm City Oil | New Haven | CT |
| Elton Hotel | Waterbury | CT |
| Ely School | Greenwich | CT |
| Emhart | Bloomfield | CT |
| Emhart | Berlin | CT |
| Empire-Ace Insulation | East Hartford | CT |
