| Miller Falls | Greenfield | ME |
| Mt. Mercy Academy | Waterville | ME |
| Nathan Clifford School | Portland | ME |
| Nathaniel Bacon | South Portland | ME |
| New England Insulation | Bangor | ME |
| New England Insulation | Portland | ME |
| New England Pipe & Supply | Bangor | ME |
| New England Shipbuilding | South Portland | ME |
| New Windham High School | Windham | ME |
| Northeast Coal & Dock | Bucksport | ME |
| Northeastern Paving | Westbrook | ME |
| Northern Chemical | Searsport | ME |
| Northern Paper Mills | Rumford | ME |
| Northern Paper Mills | Madison | ME |
| Northern Pipe & Supply | Presque Isle | ME |
| Ohemetron | Searsport | ME |
| Orono Pulp & Paper | Basin Mills | ME |
| Orono Pulp & Paper | Orono | ME |
| Otis Falls Pulp & Paper | Livermore Falls | ME |
| Otis Falls Pulp & Paper | Chisholm | ME |
| Otis Falls Pulp & Paper | Portland | ME |
| Oxford Paper | Oxford | ME |
| Oxford Paper | Rumford | ME |
| Oxford Paper | Portland | ME |
| Paris Manufacturing | South Paris | ME |
| Patrick Soucie | Caribou | ME |
| Pejepscot Paper | Lisbon Falls | ME |
| Pejepscot Paper | Brunswick | ME |
| Penobscot | Old Town | ME |
| Penobscot | Penobscot | ME |
| Penobscot | Great Works | ME |
| Pepperell Manufacturing | Biddeford | ME |
| Pineland Hospital & Training Center | Pownal | ME |
| Pine Tree Insulation | Auburn | ME |
| Pinkham Lumber | Ashland | ME |
| Poland Paper | Mechanic Falls | ME |
| Polar Chemicals - Repackaging Plant | Lewiston | ME |
| Portland Extract | Mechanic Falls | ME |
| Portland Gas & Light | Portland | ME |
| Portland High School | Portland | ME |
| Portland Iron & Steel | Portland | ME |
| Portland Lighting & Power | Portland | ME |
| Portland Railroad | Portland | ME |
| Portland Stock | Portland | ME |
| Portland Street Railway | Portland | ME |
| Portland & Yarmouth Electric Railway | Portland | ME |
| Portsmouth Naval Shipyard | Kittery | ME |
| Post Office & Federal Office Building | Augusta | ME |
| Pownal State School | Pownal | ME |
| Purplestar | South Portland | ME |
