| I & M Rail Link, LLC | IMRL | added 7/97; 7/2000 | |
| I.I. Selig & Sons Ltd. | IISX | added 10/68; 4/70; eliminated 10/70 | |
| Iberia & Vermillion R.R. | I&V | Apr-38 | |
| IBP, Inc. | IBPX | added 5/83; 1/94; eliminated 7/95 | |
| PBFX | added 7/94; 7/2000 | ||
| ICI Acrylics Inc. | CPIX | added 1/93; 1/94; eliminated 10/97; 7/2000 | |
| ICI America Inc. | ICIX | added 4/72 | |
| APCX | added 4/72 | ||
| ICI Americas Inc. | ICIX | 1/80-1/94; eliminated 4/96; 7/2000 | |
| ICI United States Inc. | ICIX | Jan-75 | |
| APCX | 1/75-1/80 | ||
| ID Packing Company, Inc. | IDEX | added 4/70; 4/70; eliminated 4/72 | |
| Idaho Northern & Pacific R.R. Co. | INPR | Jul-00 | |
| IES Utilities, Inc. | IESX | added 1/96; eliminated 4/2000 | |
| LNTX | added 4/99; eliminated 4/2000 | ||
| OGSX | added 1/96; eliminated 4/2000 | ||
| IESX Corp. | IESX | added 7/81; eliminated 10/87 | |
| Illinois & Midland R.R. Inc. | IMRR | added 7/96; 7/2000 | |
| CIM | eliminated 4/97 | ||
| Illinois Central Gulf R.R. | MSC | 1/75-1/80 | |
| Illinois Central Gulf R.R. Co. | IC | eliminated 4/88 | |
| ICG | 1/75-1/80; eliminated 4/88 | ||
| CIW | eliminated 4/88 | ||
| CLG | 1/75-1/80 | ||
| GMO | eliminated 4/88 | ||
| Illinois Central Gulf R.R. Co. (Gulf, Mobile & Ohio R.R. Co.) | GMO | 1/75-1/80 | |
| Illinois Central Gulf R.R. Co. (Illinois Central) | IC | 1/75-1/80 | |
| Illinois Central R.R. | PSL | Jul-65 | |
| Illinois Central R.R. Co. | IC | 4/38-4/70 | |
| IC | added 4/88; 1/94-7/2000 | ||
| ICG | added 4/88; 1/94-7/2000 | ||
| CIW | added 4/88; 1/94-7/2000 | ||
| GMO | added 4/88; 1/94-7/2000 | ||
| Illinois Cereal Mills, Inc. | ICMX | added 4/92; 1/94-7/2000 | |
| Illinois Northern R.R. Co. | IN | 4/38-10/66 & 1/75; eliminated 4/75 | |
| Illinois Oil Co. | IOCX | Apr-38 | |
| Illinois Power Co. | IPLX | added 1/65; 7/65-1/80; eliminated 4/89; 1/94-7/2000 | |
| Illinois RailNet, Inc. | IR | Jul-00 | |
| Illinois Steel Co. (Carnegie-Illinois Steel Corp.) | ISCX | Apr-38 | |
| Illinois Tank Line | ITLX | Apr-38 | |
| Illinois Terminal R.R. Co. | ITC | 1/52-10/66 & 1/75-1/80; eliminated 4/82 | |
| Illinois Transit Assembly Corp. | ITAX | Jul-00 | |
| Illinois Union Ry. Co. | IU | Apr-38 | |
| Illinois Western R.R. Co. | ILW | Jul-00 | |
| Illinois-Wisconsin Sand & Gravel Co. | IWSX | 1/75-1/80; eliminated 10/80 | |
| IMC Fertilizer, Inc. | IMCX | added 4/88; 1/94; eliminated 1/95 | |
| BPPX | added 4/88; 1/94; eliminated 4/94 | ||
| IMC Global Operations, Inc. | IMCX | added 1/95; 7/2000 | |
| IMCO Services, a Division of Halliburton Co. | IMSX | added 1/82; eliminated 1/86 | |
| Imperial Oil, Ltd. | IOX | Apr-38 | |
| COBX | Apr-38 | ||
| Imperial Refineries | IMRX | Apr-38 | |
| Imperial Refineries Corp. | IMRX | added 7/55; 10/57 | |
| Imperial Sugar Co. | ISCX | added 7/60 | |
| Incan Superior Ltd. | NCAN | 1/75-1/80 | |
| Incandescent Lamp Department of General Electric Co. | ILDX | Apr-38 | |
| Incandescent Lamp Division of General Electric Co. | ILDX | Oct-66 | |
| Inco Ltd. | INCX | added 4/90; 1/94-7/2000 | |
| Incoal Co. | INLX | added 10/88; 1/94-7/2000 | |
| Incobrase Industries, Ltd. | BRIX | added 4/97; 7/2000 | |
| IND/AG Chemicals, Inc. | SNFX | added 1/83; 1/94-7/2000 | |
| SNHX | added 1/83; 1/94-7/2000 | ||
| Indeck Power Equipment, Co. | IPEX | added 4/97; 7/2000 | |
| Indelpro, S.A. de C.V. | INDX | Jul-00 | |
| Independent Locomotive Service, Inc. | ILSX | Jul-00 | |
| Indian Creek R.R. Co. | ICRK | eliminated 1/90; 1/94-7/2000 | |
| Indiana & Michigan Electric Co. | IMEX | 1/52-4/61; added 10/70; 1/75-7/2000 | |
| Indiana & Ohio Rail Corp. | INOX | added 1/95; 7/2000 | |
| Indiana & Ohio Rail System | IOER | eliminated 10/94 | |
| Indiana Boxcar Corp. | IBCX | Jul-00 | |
| Indiana Farm Bureau Cooperative Association, Inc. | IFBX | added 7/79; 1/80; eliminated 4/90 | |
| Indiana Harbor Belt R.R. Co. | IHB | 1/75-7/2000 | |
| Indiana Hi-Rail Corp. | IHRC | added 4/82; 1/94; eliminated 1/95 | |
| IHRC | added 4/95; eliminated 7/98; 7/2000 | ||
| GSOR | added 4/86; 1/94; eliminated 1/95 | ||
| GSOR | added 7/95; eliminated 7/98; 7/2000 | ||
| Indiana Interstate Ry. Co., Inc. | IIRC | added 4/78; 1/80; added 7/80; eliminated 1/83 | |
| Indiana Midland Ry. | IMID | added 4/85; eliminated 1/88 | |
| Indiana Northeastern R.R. Co. | IN | added 7/93; 1/94-7/2000 | |
| Indiana Northwestern R.R. Co. | IN | added 4/93; eliminated 7/93 | |
| Indiana Southern R.R. Co., Inc. | ISRR | added 10/92; eliminated 10/93; 1/94; added 7/96; 7/2000 | |
| Indiana Southwestern Ry. Co. | ISW | Jul-00 | |
| Indianapolis Power & Light Co. | EWSX | added 4/73; 1/75-7/2000 | |
| Indianapolis Union | IU | Jul-00 | |
| Indianapolis Union Ry. | IU | 1/52-1/94; eliminated 1/98 | |
| INDSPEC Chemical Corp. | KGCX | added 10/89; 1/94; eliminated 1/98; 7/2000 | |
| Industria del Alcali, S.A. | IDAX | added 4/74; 1/75-1/94 | |
| Industria Minera Mexico, S.A. (reporting marks being changed to IMMX) | ASMX | added 7/75 | |
| Industria Quimica Del Istmo S.A. de C.V. | IQIX | added 7/2000; 7/2000 | |
| Industrial Air Products Co. | IAPX | added 10/65; 10/66-4/70 | |
| Industrial Fuel Oil, Inc. | IFOX | added 1/81; eliminated 1/87 | |
| Industrial Minera Mexico, S.A. | IMMX | added 7/75; 1/80; eliminated 5/83; 1/94-7/2000 | |
| Industrial Oil Corp. | INDX | Apr-38 | |
| Industrial Propane Supply, Inc. | INDX | 7/65-4/70; eliminated 7/74 | |
| Industrial Steam Products | IGPX | Jul-00 | |
| Industrias Unidas de Nuevo Laredo, S.A. | IUX | 1/52-7/65; eliminated 10/65 | |
| Industry Financial Corp. | SBGX | eliminated 7/92 | |
| Industry Leasing, Inc. | SBGX | added 1/77; 1/80 | |
| Infineum USA L.P. | INFX | added 1/2000; 7/2000 | |
| Ingomar Packing Co. | INGX | 1/94; eliminated 10/94 | |
| Inland Cement Ltd. | PWCX | Jul-00 | |
| Inland Molasses Co. | ILX | Jan-52 | |
| Inland Steel Co. | INLX | added 7/68; 4/70-1/75 | |
| INLX | eliminated 10/88 | ||
| Inland Steel Coal Co. | INLX | Jan-80 | |
| Inland Waterways Corp. | IWC | Jan-52 | |
| Inspiration Consolidated Copper Co. | ICCX | added 7/74; 1/75; eliminated 10/78 | |
| Interail, Inc. | GGIX | added 7/95; eliminated 7/96 | |
| RILX | added 7/80; 1/94; eliminated 7/96 | ||
| Interall Holdings, Inc. | MITX | added 10/60; 4/61 | |
| Intercoastal Leasing, Inc. | ICLX | added 4/96; 7/2000 | |
| Interlake Iron Corp. | IICX | 1/52-4/61; eliminated 7/65 (reporting marks changed to ISCX) | |
| Interlake Iron Corp. (Toledo Furnace Plant) | IICX | Apr-38 | |
| Interlake Steel Corp. | ISCX | added 7/65 (reporting marks changed from IICX); 7/65-10/66; eliminated 10/67 | |
| Interlake, Inc. | ISCX | added 4/71; 1/75; eliminated 7/76 | |
| Intermodal Technologies Inc. | ITIX | 1/94-7/2000 | |
| Intermountain Power Agency | IPPX | added 1/85; eliminated 4/85; added 1/86; 1/94; eliminated 7/99; 7/2000 | |
| Intermountain Western R.R. | IWRR | Jan-94 | |
| International Agricultural Corp. | ITX | Apr-38 | |
| International Bridge & Terminal Co. | IBT | 1/75-1/94; added 7/98; 7/2000 | |
| International Harvester Co. | IHCX | 1/52-7/65; eliminated 10/65 | |
| International Latex Corp. | ILCX | added 7/60; 4/61; added 7/64; 7/65-10/66; eliminated 10/68 | |
| International Minerals & Chemical Corp. | IMCX | added 4/67; 4/70-1/80; eliminated 4/88 | |
| BPPX | eliminated 4/88 | ||
| International Molasses Corp. Ltd. | MOLX | added 1/98; eliminated 4/98; 7/2000 | |
| International Paper Co. | IPCX | 4/38-1/80; eliminated 10/81; added 10/84; 1/94-7/2000 | |
| International Paper Co. | FPBX | added 4/99; 7/2000 | |
| HPAX | added 1/92; 1/94-7/2000 | ||
| International Rail Road Systems, Inc. | IRRS | Jul-00 | |
| International Railway Car & Equipment Co. | IRCX | Jan-52 | |
| International Railway Car Co. | IRCX | 10/57; eliminated 1/59 | |
| International Railway Car Leasing Co. | IRCX | added 1/59; 4/61; eliminated 1/62 | |
| International Sugar Co. | ISCX | eliminated 10/60 | |
| International Technologies Corp. | ITCX | Jul-00 | |
| International Transport Co. | ITLX | added 1/74; 1/75; eliminated 4/79 | |
| International-Great Northern R.R. | IGN | 4/38-7/65 & 1/75-1/80 | |
| Interstate Foods Corp. | IFCX | added 10/82; 1/94; eliminated 10/94; 7/2000 | |
| Interstate Power Co. | IPWX | added 7/79; 1/80-1/94; eliminated 4/2000 | |
| Interstate R.R. | INT | 4/38-10/66 & 1/75-1/80 | |
| Interstate Tank Car Corp. | ISTX | 4/38-10/57; eliminated 10/59 | |
| Interstate Transport Co. | ITCX | 4/38-4/61 | |
| Investor's Property Service | BENX | Jul-00 | |
| Iowa Interstate R.R., Ltd. | IAIS | added 1/85; 1/94-7/2000 | |
| Iowa Northern Ry. | IANR | added 1/82; 1/94-7/2000 | |
| Iowa Power & Light Co. | IOPX | 1/80; eliminated 4/93 | |
| Iowa Public Service Co. | TRIX | added 7/75; 1/80 | |
| Iowa R.R. Co. | IRRC | added 1/82; eliminated 4/88 | |
| Iowa Southern R.R. Co. | ISR | added 10/87; eliminated 4/90; 1/94-7/2000 | |
| Iowa Southern Utilities (Southern Industrial R.R., Inc.) | ISU | 1/75-1/80 | |
| Iowa Southern Utilities Co. | IESX | eliminated 1/96 | |
| ISN | Apr-38 | ||
| ISU | Jan-52 | ||
| OGSX | added 7/80; 1/94; eliminated 1/96 | ||
| Iowa Terminal R.R. Co. | IAT | 1/75-1/80; added 10/80; eliminated 7/87 | |
| Iowa Traction R.R. Co. | IAT | added 7/87; eliminated 1/88 | |
| IATR | added 7/87; 1/94-7/2000 | ||
| Iowa-Gas & Electric Co. | WRDX | added 10/83; 1/94 | |
| Iowa-Illinois Gas & Electric Co. | WRDX | added 10/82 | |
| WRDX | eliminated 4/96 | ||
| IRECO, Inc. | IREX | added 10/86; eliminated 1/94; 7/2000 | |
| Iron & Steel Products Inc. | ISPX | Jan-52 | |
| Ironton R.R. Co. | IRN | 4/38-10/66 & 1/75; eliminated 4/76 | |
| ISC, Inc. | ISCX | 1/94-7/2000 | |
| ISG Resources, Inc. | JTMX | Jul-00 | |
| Island Creek Coal Co. | ICRX | added 1/79; 1/80; eliminated 7/89 | |
| Island Creek Corp. | ICRX | added 7/89; 1/94-7/2000 | |
| IRCX | eliminated 7/97 | ||
| Island Tug & Barge | ITB | 1/75-7/2000 | |
| ISS Rail, Inc. | ISSR | added 10/93; 1/94-7/2000 | |
| Itel Corp., Rail Division | SSIX | added 1/78; 1/80; eliminated 4/87 | |
| Itel Rail Corp. | ITLX | eliminated 10/92 | |
| DSDX | added 1/90; eliminated 10/92 | ||
| EELX | added 4/88; eliminated 10/92 | ||
| ERLX | added 4/88; eliminated 10/92 | ||
| LRLX | added 4/88; eliminated 10/92 | ||
| MRCX | added 4/88; eliminated 10/92 | ||
| PLCX | added 1/90; eliminated 10/92 | ||
| PLWX | added 1/90; eliminated 10/92 | ||
| PTLX | added 1/90; eliminated 10/92 | ||
| RREX | eliminated 10/92 | ||
| RRRX | eliminated 10/92 | ||
| RSPX | added 4/88; eliminated 10/92 | ||
| SSIX | added 4/87; eliminated 10/92 | ||
| TLCX | added 1/90; eliminated 10/92 | ||
| TLDX | added 1/90; eliminated 10/92 | ||
| USEX | added 4/88; eliminated 10/92 | ||
| USLX | added 4/88; eliminated 10/92 | ||
| WFIX | added 1/90; eliminated 10/92 | ||
| ITG Inc. | ITGX | eliminated 1/87; 1/94-7/2000; eliminated 7/2001 | |
| Ivan E. Summa | IESX | added 4/74; 1/75-1/80; eliminated 7/81 | |