| Abbreviation | Definition |
|---|---|
| INKU | Interpool Limited |
| INLX | Incoal Company |
| INLX | Inland Steel Coal (Incoal) |
| INMZ | Inglehand Minerals and Chemicals |
| INNU | Seacube Container Leasing |
| INOH | Indiana and Ohio Railroad |
| INOH | Indiana and Ohio Railroad Incorporated |
| INOX | Indiana and Ohio Rail Corporation |
| INPR | Idaho Northern and Pacific Railroad |
| INPR | Idaho Northern Pacific Railroad |
| INRD | Indiana Rail Road Company |
| INRD | Indiana Railroad |
| INRR | Idaho Northern RailRoad |
| INRR | Indiana Northeastern RailRoad |
| INRX | International Refining Company |
| INRY | Illinois Northern Railway |
| INS | Inland Steel (now ISPX - ISPAT Inland, Inc.) |
| INSU | Intersub Services |
| INSX | Independent Salt |
| INT | Interstate Railroad (Norfolk Southern) |