| Abbreviation | Definition |
|---|---|
| ACCX | Consolidation Coal Company |
| ACDX | Allied Chemical Company (Allied Corporation) |
| ACDX | Allied Chemical Corporation (Honeywell International) |
| ACE | Ashepoo, Combahee, and Edisto Railroad |
| ACEX | Ace Cogeneration Company |
| ACEX | Atlantic City Electric Power |
| ACFX | American Car and Foundry |
| ACFX | American Car and Foundry (General Electric Rail Services Corporation) |
| ACFX | General Electric Railcar Services Corporation |
| ACGX | Acme Gas Corporation (Suburban Propane) |
| ACGX | Suburban Propane LP |
| ACHR | Algoma Central & Hudson Bay Railway |
| ACHX | American Cyanamid Company |
| ACIS | Algoma Central Railway |
| ACIS | Algoma Central Railway Incorporated |
| ACIU | Allstate Container |
| ACIX | Arkansas Chemicals (Great Lakes Chemical Corporation) |
| ACIX | Great Lakes Chemical Corporation |
| ACJR | Ashtabula Carson Jefferson Railroad Company |
| ACJR | Ashtabula, Carson and Jefferson Railroad |