| 1 | MHHC | MERRITT HEAVY HAUL LLC | | | SCAC4 |
| 2 | MHHI | MATES HEAVY HAUL INC | | | SCAC4 |
| 3 | MHHL | MILLS HEAVY HAULING LIMITED | | | SCAC4 |
| 4 | MHHR | Mahanoy and Hazleton Ry., Inc. | added 7/1985; eliminated 10/1986 | | NAKINA |
| 5 | MHHR | MAHANOY & HAZLETON RWY., INC. | | | PWRC |
| 6 | MHHT | MACHINERY TRANSPORT INC | | | SCAC4 |
| 7 | MHHU | MAERSK A/S | | DK | BIC |
| 8 | MHHU | A P MOLLER | | | SCAC4 |
| 9 | MHHV | MARKS HEAVY HAULING & EXCAV INC | | | SCAC4 |
| 10 | MHHX | Mohawk & Hudson Chapter, National Railway Historical Society | added 10/2003; eliminated 1/2004; 7/2005 (not listed) | | NAKINA |
| 11 | MHHX | MOHAWK & HUDSON CHAPTER, NATIONAL RAILWAY HISTORICAL SOCIETY | | | PWRC |
| 12 | MHHX | MOHAWK & HUDSON CHAPTER NATIONAL RA | | | SCAC4 |
