| Pratt & Whitney Aircraft | Windsor | CT |
| Pratt & Whitney Aircraft | Middletown | CT |
| Pratt Whitney Aircraft | Middletown | CT |
| Princeton | Watertown | CT |
| Producto Machine | Bridgeport | CT |
| Products Machine | Bridgeport | CT |
| Public Siding | Naugatuck | CT |
| Putnam-Herzl Finishing | Putnam | CT |
| Quinebaug | Danielson | CT |
| Quinnipiac Energy LLC | New Haven | CT |
| Randolph Clowes | Waterbury | CT |
| Rann Hickman Associates | Bridgeport | CT |
| Raybestos | Stratford | CT |
| Raybestos | Bridgeport | CT |
| Raybestos | Milford | CT |
| Raymark | Stratford | CT |
| Read D M | Bridgeport | CT |
| Read & Greenwood | Meriden | CT |
| Read School | Bridgeport | CT |
| Reed & Greenwood | Hartford | CT |
| Reed & Greenwood | East Hartford | CT |
| Remington Arms | Bridgeport | CT |
| Remington Arms | Stratford | CT |
| Remington Noiseless Typewriter | Middletown | CT |
| Remington Rand | Bridgeport | CT |
| Republic Steel | Hartford | CT |
| Resource Recovery Systems | Hartford | CT |
| Rex Forge | Plantsville | CT |
| Richards & Company | Stamford | CT |
| Riggs Distler & Company | Hartford | CT |
| Riley Stoker | Essex | CT |
| Riverton Paper | Winsted | CT |
| R.J. Kinsella Magnet School Of Performing Arts | Hartford | CT |
| R. L. Dingee Enterprises | Danbury | CT |
| Robert A. Keasbey | Bridgeport | CT |
| Robert Gair | Montville | CT |
| Robertshaw Controls | Milford | CT |
| Robertson Paper Box | Montville | CT |
| Rockville & Ellington Street Railway | Rockville | CT |
| Rockville Worsted | Rockville | CT |
| Rockwell Manufacturing | Fairfield | CT |
| Rockwell Stanley P | Hartford | CT |
| Rockwell W S | Fairfield | CT |
| Rogers | East Woodstock | CT |
| Rogers Company | Rogers | CT |
| Rogers Paper Manufacturing | Dayville | CT |
| Rolock | Fairfield | CT |
| Rose Street Power House | New Haven | CT |
| Roton Junior School | Bridgeport | CT |
| Royalmetal | Plainfield | CT |
