| Isaac Sharpless | South Portland | ME |
| James River | Old Town | ME |
| James Sullivan | South Portland | ME |
| Jas. P. Baxter | Portland | ME |
| Jay Paper Mill | Jay | ME |
| Joseph C. Lincoln | South Portland | ME |
| Katahdin Pulp & Paper Mill | Lincoln | ME |
| Keddy Manufacturing | Windham | ME |
| Kennebec Pulp & Paper | Augusta | ME |
| Kennebec Pulp & Paper | Madison | ME |
| Keyes Fibre | Waterville | ME |
| Keyes Fibre | Shawmut | ME |
| KTI | Biddeford | ME |
| Kuhr Technologies | Biddeford | ME |
| Lewiston & Auburn Street Railway | Lewiston | ME |
| Lewiston & Auburn Street Railway | Freeport | ME |
| Lewiston Brunswich & Bath Street Railway | Lewiston | ME |
| Lewiston Gas Light | Lewiston | ME |
| LFC Power Systems | Lewiston | ME |
| Lincoln Pulp & Paper | Lincoln | ME |
| Lincoln Pulp & Paper | Millinocket | ME |
| Lockwood | Waterville | ME |
| Loring Air Force Base | Limestone | ME |
| Lot M Morrill | South Portland | ME |
| Madison Paper | Madison | ME |
| Maine Central Railroad | Portland | ME |
| Maine Central Railroad | Waterville | ME |
| Maine Energy Recovery | Biddeford | ME |
| Maine Eye & Ear Infirmary | Portland | ME |
| Maine Maritime Academy | Castine | ME |
| Maine Medical Center | Portland | ME |
| Maine Public Service | Caribou | ME |
| Maine Seaboard Paper | Bucksport | ME |
| Maine State Cultural Building | Augusta | ME |
| Maine State Prison | Thomaston | ME |
| Maine Yankee Atomic Power | Wiscasset | ME |
| Maple Street Siding | Portland | ME |
| Maplewood Poultry | Belfast | ME |
| Marcal Paper | Mechanic Falls | ME |
| Marcus H Tracy | South Portland | ME |
| Maria De Larrinaga | South Portland | ME |
| Marine Colloids | Rockland | ME |
| Marine Transport | Portland | ME |
| Martin Marietta Cement | Thomaston | ME |
| Masonic Building | Portland | ME |
| Masonite | Lisbon Falls | ME |
| Mead Paper | Rumford | ME |
| Mechanical Services | Portland | ME |
| Meletios | South Portland | ME |
| Merchants National Bank | Bangor | ME |
