| Hartford Steam | Hartford | CT |
| Harvey Hubel | Bridgeport | CT |
| Hendey Machine | Torrington | CT |
| Henry Griffin Pottery | West Haven | CT |
| Heppenstall | Bridgeport | CT |
| Herpenstall | Bridgeport | CT |
| Hess Oil | Wethersfield | CT |
| Hess Oil | Groton | CT |
| Heublein | Hartford | CT |
| High Ridge Park | Stamford | CT |
| High Rise Elderly Housing | Hartford | CT |
| High Standard Manufacturing | Hamden | CT |
| Hitchiner Manufacturing | Wallingford | CT |
| Hockanum Mills | Rockville | CT |
| Holiday Inn | Norwalk | CT |
| Holmes, Booth & Haydens | Waterbury | CT |
| Homelite Factory | Greenwich | CT |
| Homestead Insulation | East Hartford | CT |
| Homestead Insulation | Hartford | CT |
| Homestead Insulation | Windsor Locks | CT |
| Homestead Stores | East Hartford | CT |
| Hotchkiss School | Lakeville | CT |
| Hotel America | Hartford | CT |
| Hotel Taft | New Haven | CT |
| Housatonic Power | Waterbury | CT |
| Housatonic Public Service | Derby | CT |
| Housatonic Valley Ref | Falls Village | CT |
| Housing for the Elderly | Bridgeport | CT |
| Howard Johnson Restaurant | Wethersfield | CT |
| Hoyt Grant | New Haven | CT |
| Hp Hood | Suffield | CT |
| Hublein | Hartford | CT |
| Hydro-Blast | Bridgeport | CT |
| Ideal Plumbing & Heating | New Haven | CT |
| Illuminating | New Haven | CT |
| Industrial Refractories | Bridgeport | CT |
| Infield Metals | Waterbury | CT |
| Insulation | West Hartford | CT |
| Insulation Supply | Orange | CT |
| International Paper | Versailles | CT |
| International Silver | Meriden | CT |
| International Silver | Wallingford | CT |
| Interstate Container | New Haven | CT |
| Inverform #1 | Versailles | CT |
| Isolation Hospital | Bridgeport | CT |
| Jack W. Straub | New Milford | CT |
| Jack W Stroab | New Milford | CT |
| James J. Regan Manufacturing | Rockville | CT |
| James L. Howard & Company | Hartford | CT |
| James V. Ursini | New Haven | CT |
