| J.B. Martin | Norwich | CT |
| J.B. Williams | Glastonbury | CT |
| Jelliff | Southport | CT |
| Jenkins Brothers | Bridgeport | CT |
| Jewish Community Center | Bridgeport | CT |
| Jewish Community Center | Woodbridge | CT |
| J.H. Sessions & Sons | Bristol | CT |
| J. M Delaney | Meriden | CT |
| Johnson Carlyle Machine C | Manchester | CT |
| Kaman | Bloomfield | CT |
| Kaman Aerospace | Windsor | CT |
| Kanthal | Bethel | CT |
| Kelsey Ferguson Brick Plant | Hartford | CT |
| Kennecott Copper | Waterbury | CT |
| Kennedy Apartments | Bristol | CT |
| Kerite | Seymour | CT |
| Kerite Insulated Wire & Cable | Seymour | CT |
| Kimberly & Clark | New Milford | CT |
| King Industries | Norwalk | CT |
| King Organic Chemicals | Norwalk | CT |
| King Seeley Thermos | Norwich | CT |
| Kline Geology Lab | New Haven | CT |
| Knights Of Columbus | New Haven | CT |
| Knolls Atomic Nuclear Plant | Windsor | CT |
| Kolpak | New Britain | CT |
| Koppers | Cromwell | CT |
| Kramer Iron Works | Hamden | CT |
| Krantz Express & Warehouse | East Hartford | CT |
| Labor Department Building | Wethersfield | CT |
| Labor Department Building | Hartford | CT |
| Lafayette Bank & Trust | Bridgeport | CT |
| Landers, Frary & Clark | New Britain | CT |
| Landmark Tower | Stamford | CT |
| Lane Construction | Meriden | CT |
| Largo Properties Office | Stamford | CT |
| Lawrence & Memorial Hospital | New London | CT |
| Lawton Mills | Plainfield | CT |
| L.D. Brown & Son | Middletown | CT |
| Lee High School | New Haven | CT |
| Leppert Nutmeg, Incoroporated | Hartford | CT |
| Lewin & Sons | Bridgeport | CT |
| Lewis Batchelder School | Hartford | CT |
| Liberty Ordnance | Bridgeport | CT |
| Limback | Hartford | CT |
| Linde Air Products | New Haven | CT |
| Litchfield High School | Bridgeport | CT |
| Litchfield Junior High School | Bridgeport | CT |
| Locke Manufacturing | Bridgeport | CT |
| Lombardi Manufacturing | Derby | CT |
| Louise Duffy School | West Hartford | CT |
