| Raymond B. Stevens | South Portland | ME |
| Rio Grande | South Portland | ME |
| R.J. Peacock Canning | Portland | ME |
| Robinson Kenney | Brewer | ME |
| Saco Lowell Shops | Biddeford | ME |
| Saco Tanning Plant | Saco | ME |
| Saint Croix Paper | Woodland | ME |
| Saint Regis Paper | Bucksport | ME |
| Samadang | South Portland | ME |
| Samadre | South Portland | ME |
| S.A. Maxfield | Bangor | ME |
| Sambanka | South Portland | ME |
| Samidway | South Portland | ME |
| Samoresay | South Portland | ME |
| Samsuva | South Portland | ME |
| Samwake | South Portland | ME |
| Sanford Mills | Sanford | ME |
| Sanford Sheet Plant | Sanford | ME |
| Sappi Fine Papers | Westbrook | ME |
| Sappi Fine Papers | Skowhegan | ME |
| Saraya | South Portland | ME |
| Scott Paper | Skowhegan | ME |
| Scott Paper | Hinckley | ME |
| Scott Paper | Westbrook | ME |
| Scott Paper | Winslow | ME |
| S. D. Warren | Hinckley | ME |
| S. D. Warren | Westbrook | ME |
| S. D. Warren | Skowhegan | ME |
| S. D. Warren | Gardiner | ME |
| Seacoast Canning | Eastport | ME |
| Seacoast Canning | Lubec | ME |
| Seton Hospital | Waterville | ME |
| Simplex Wire & Cable | North Berwick | ME |
| Somerset | Skowhegan | ME |
| Somerset | Fairfield | ME |
| South Portland Dry Dock & Repair | South Portland | ME |
| South Portland Shipyard | Portland | ME |
| South Portland Shipyard | South Portland | ME |
| Sprague & Sons Plant | Searsport | ME |
| Standard Packaging | Lincoln | ME |
| State Of Maine | Augusta | ME |
| State Teachers College | Machias | ME |
| Statler Tissue | Augusta | ME |
| Swift River Hafslund | Greenville | ME |
| Sylvania Electric | Waldoboro | ME |
| Taterstate Frozen Foods | Washburn | ME |
| Texaco | South Portland | ME |
| Texas Steamship | Bath | ME |
| Texas Towers 1 | South Portland | ME |
| Texas Towers 2 | South Portland | ME |
