| 1 | MCR | Monacair-Agusta | Callsign: Monacair, | MC | AVCODES |
| 2 | MCR | McCloud Ry. Co. | 1/1994-7/2005 | | NAKINA |
| 3 | MCR | McCloud River Ry. Co. | 1/1975-1/1980 | | NAKINA |
| 4 | MCR | McCloud River Ry. Co. | 1/75-1/80 | | NRHS |
| 5 | MCR | McCloud Ry. Co. | 1/94-7/2000 | | NRHS |
| 6 | MCR | MCCLOUD RAILWAY COMPANY [MCCLOUD RIVER RWY. CO.] | | | PWRC |
| 7 | MCR | McCloud River Railroad (McCloud Railway) | | | RSRV |
| 8 | MCR | MCCLOUD RAILWAY COMPANY | | | SCAC4 |
| 9 | MCR | McCloud River Railway Company | | USA | TRAFFIC |
| 10 | MCRC | MCR PRINTING AND PACKAGING CORP | | | SCAC4 |
| 11 | MCRE | MCCARTNEY, KEITH | | | SCAC4 |
| 12 | MCRF | MEDINA CORTEZ, EFREN | | | SCAC4 |
| 13 | MCRI | MARSH, CARL R TRUCKING LLC | | | SCAC4 |
| 14 | MCRJ | MERCER TRANSPORT LLC | | | SCAC4 |
| 15 | MCRK | MCCRACK | | | SCAC4 |
| 16 | MCRM | MID CONTINENT MUSEUM | | | PWRC |
| 17 | MCRM | MCCORMI | | | SCAC4 |
| 18 | MCRO | MARTINEZ CHAPA, REYNOL | | | SCAC4 |
| 19 | MCRR | The Monongahela Connecting R.R. Co. | 1/1975-7/2000; eliminated 1/2003; 7/2005 | | NAKINA |
| 20 | MCRR | The Monongahela Connecting R.R. Co. | 1/75-7/2000 | | NRHS |
| 21 | MCRR | MONONGAHELA CONNECTING RAILROAD CO. | | | PWRC |
| 22 | MCRR | Monongahela Connecting Railroad | | | RSRV |
| 23 | MCRR | MCRORIE, RICKARD B | | | SCAC4 |
| 24 | MCRR | The Monongahela Connecting R.R. Co. | | USA | TRAFFIC |
| 25 | MCRS | MACRIS EXPRESS INC | | | SCAC4 |
| 26 | MCRT | MCLAUGHLIN ROOF TRUSSES LTD | | | SCAC4 |
| 27 | MCRU | MAERSK A/S | | DK | BIC |
| 28 | MCRU | A P MOLLER | | | SCAC4 |
| 29 | MCRV | MARCARE TRUST 1259 | | | SCAC4 |
| 30 | MCRW | MAINLY CONVERTIBLES | | | SCAC4 |
| 31 | MCRW | Maine Coast R.R. Corp. | Real: MCRR | USA | TRAFFIC |
| 32 | MCRX | Marcus Rail Transport, L.L.C. | 7/2000-7/2005 (not listed) | | NAKINA |
| 33 | MCRX | McCook Rendering Co. | 4/1947 (not listed); 1/1950-10/1957; eliminated 1/1958 | | NAKINA |
| 34 | MCRX | McCook Rendering Plant | Jan-52 | | NRHS |
| 35 | MCRX | McCook Rendering Co. | 10/57; eliminated 1/58 | | NRHS |
| 36 | MCRX | Marcus Rail Transport, L.L.C. | Jul-00 | | NRHS |
| 37 | MCRX | *MCCOOK RENDERING CO. | | | PWRC |
| 38 | MCRX | *MORRISON COVE RAILROAD | | | PWRC |
| 39 | MCRX | +MARCUS RAIL TRANSPORT [MARCUS CORPORATION] | | | PWRC |
| 40 | MCRX | Marcus Rail Transport | | | RSRV |
| 41 | MCRX | MARCUS RAIL TRANSPORT LLC | | | SCAC4 |
| 42 | MCRY | MID CONTINENT RAILWAY | | | PWRC |
| 43 | MCRY | Mid Continent Railway | | | RSRV |
| 44 | MCRY | MERCURY COURIER INC | | | SCAC4 |
