| 1 | MPP | MANITOU & PIKE'S PEAK RAILROAD CO. | | | PWRC |
| 2 | MPPD | MARSHALL, PAUL PRODUCE INC | | | SCAC4 |
| 3 | MPPE | MID PAC PETROLEUM LLCGOLD BOND BUIL | | | SCAC4 |
| 4 | MPPN | MEDPARTS PLUS INC | | | SCAC4 |
| 5 | MPPT | MOORE PETROLEUM PRODUCTS | | | SCAC4 |
| 6 | MPPW | MPP CONTAINER AS | | | SCAC4 |
| 7 | MPPX | Montana Phosphate Products Co. | added 7/1955; eliminated 4/1956 | | NAKINA |
| 8 | MPPX | Montana Phosphate Products Co. | added 7/55 | | NRHS |
| 9 | MPPX | MONTANA PHOSPHATE PRODUCTS CO. | | | PWRC |
| 10 | MPPY | METRO PARTS COMPANY | | | SCAC4 |
| 11 | MPPZ | MOBA POWER PLANT | | | PWRC |
