| SA | Savannah & Atlanta Ry. Co. | 4/38-4/70 |
| Central of Georgia R.R. Co. | 1/75-1/80 | |
| Southern Ry. System | eliminated 1/91 | |
| Norfolk Southern Ry. Co. | added 1/91; 1/94-7/2000 | |
| SAAP | San Antonia and Aransas Pass Ry. (Southern Pacific Lines in Texas and Louisiana) | 4/38-1/52 |
| SABX | Southern Advance Bag & Paper Co. | eliminated 7/55 |
| Southern Advance Bag & Paper Division of Robert Gair Co., Inc. | added 7/55 | |
| Continental Can Co., Inc. | Oct-57 | |
| Continental Can Co., Inc., Southern Advance Paper Operation | eliminated 10/59 | |
| Continental Can Co., Inc. | added 10/59; 4/61-4/70; eliminated 4/74 | |
| SAC | Southern Alkali Corp. | Apr-38 |
| SACX | Columbia-Southern Chemical Corp. | 1/52-10/57; eliminated 4/61 |
| Pittsburgh Plate Glass Co. | added 4/61; 4/61-10/66; eliminated 4/68 | |
| PPG Industries, Inc. | added 4/68; 4/70; eliminated 10/72 | |
| SAFX | Safety-Kleen Corp. | added 4/97; 7/2000 |
| SAGX | The Smith Agricultural Chemical Co. | Apr-38 |
| SAL | Seaboard Coast Line R.R. Co. | 1/75-1/80; eliminated 1/83 |
| Seaboard System R.R., Inc. | added 1/83; eliminated 7/87 | |
| CSX Transportation, Inc. | added 7/87; 1/94-7/2000 | |
| SALX | General American Marks Co. | added 7/99; 7/2000 |
| SAMX | Seaboard Allied Milling Corp. | added 1/81; eliminated 4/82 |
| Seaboard Allied Milling Dept. of Cargill, Inc. | added 4/82; eliminated 7/84 | |
| Cargill, Inc. | added 7/84; 1/94-7/2000 | |
| SAN | Sandersville R.R. Co. | 7/65-1/94; added 4/97; 7/2000 |
| SANX | San Angelo Tank Car Line | 10/57-7/2000 |
| SAPT | Savannah Port Terminal R.R., Inc. | added 10/98; 7/2000 |
| SAQX | Southern Agricultural Tank Line | Apr-38 |
| SARX | Salyer Refining Co., Inc. | Jan-52 |
| Southern Appalachia Railway Museum | Jul-00 | |
| SASX | Southern Acid & Sulphur Co., Inc. | Apr-38 |
| Mathieson Chemical Corp. | Jan-52 | |
| Olin Mathieson Chemical Corp. | 10/57-4/61; eliminated 7/65 | |
| Suburban Fuel Tank Car Co. | added 7/65; 7/65-1/75; eliminated 1/79 | |
| Continental Tank Car Corp. | added 1/79; 1/80; eliminated 7/82 | |
| SATX | Standard Acid Works, Inc. (Standard Wholesale Phosphate & Acid Works, Inc.) | Apr-38 |
| City Public Service Board of San Antonio, Texas | 1/80-7/2000; eliminated 4/2001 | |
| City Public Service of San Antonio, Texas | added 4/2001 | |
| SAUX | Sauvage Gas Co. | added 1/65; 7/65-7/2000 |
| SAVX | Savannah Electric and Power Co. | added 10/96; 7/2000 |
| SAW | South Plains Switching Ltd. Co. | Jul-00 |
| SAWX | SAWCO, Inc. | eliminated 4/91 |
| Sawyer Gas of Jacksonville, Inc. | added 4/91; 1/94; eliminated 10/98; 7/2000 | |
| SAX | Simmons Oil & Refining Co. | 4/38-10/57 |
| Simmons Oil Corp. | Apr-61 | |
| SAZX | Saz Corp. | added 7/79; 1/80; eliminated 4/80 |
| Saz Transportation Corp. | added 4/80; 1/94-7/2000 | |
| SB | South Buffalo Ry. Co. | 1/52-1/94; eliminated 10/99; 7/2000 |
| SBC | Ferrocarril Sonora Baja California, S.A. de C.V. | 1/75-1/80 |
| Ferrocarril Sonora Baja California, S.A. de C.V. (transferred to Ferrocarriles Nacionales de Mexico) | eliminated 10/88 | |
| Ferrocarriles Nacionales de Mexico | added 10/88; 1/94-7/2000 | |
| SBCX | Armour Car Lines | added 1/60; 4/61 |
| North American Car Corp. | added 7/68; 4/70-1/75; eliminated 4/75 | |
| SBD | Seaboard System R.R., Inc. | added 1/83; eliminated 7/87 |
| CSX Transportation, Inc. | added 7/87; 1/94-7/2000 | |
| SBGX | NYTCO Leasing, Inc. | added 11/73; 1/75 |
| Transport Leasing Corp. | eliminated 1/77 | |
| Industry Leasing, Inc. | added 1/77; 1/80 | |
| Industry Financial Corp. | eliminated 7/92 | |
| SBIX | Standard Brands Inc., Tank Car Division | 1/52-10/66; eliminated 4/70 |
| Standard Brands Inc. | added 4/70; 1/75-1/80; eliminated 4/80 | |
| SBK | South Brooklyn Ry. Co. | 4/38-1/80; eliminated 10/92; 1/94 |
| SBLN | Sterling Belt Line Ry. | 1/94-7/2000 |
| SBLX | Sunbelt Chlor/Alkali Partnership | added 7/97; 7/2000 |
| SB&M | St. Louis, Brownsville & Mexico Ry. | 4/38-4/70 |
| SBM | St. Louis, Brownsville & Mexico | 1/75-1/80 |
| SBOX | Sherwood Brothers, Inc. | Apr-38 |
| SBPX | Koppers Co. | Apr-38 |
| SB&R | San Benito & Rio Grande Valley Ry. | 4/38-1/52 |
| SBRR | Stourbridge R.R. Co. | added 1/90; 1/94-7/2000 |
| SBVR | South Branch Valley Rail Road | added 10/78; eliminated 1/79; 1/80-7/2000 |
| SC | Sumter & Choctaw Ry. Co. | 1/75-1/80; eliminated 1/86 |
| SCAX | Shell Oil Co. of Canada, Ltd. | 4/38-1/52; eliminated 7/56 |
| Union Tank Car Co. | added 7/56; 10/57; eliminated 1/58 | |
| Shell Canada Ltd. | added 4/67; 4/70-1/80; eliminated 7/81 | |
| SCBG | Santa Cruz, Big Trees & Pacific Ry. Co. | 1/94-7/2000 |
| SCBX | Shell Oil Co. of British Columbia, Ltd. | Apr-38 |
| Standbridge Color Corp. | added 7/97; 7/2000 | |
| SCCX | Shell Oil Co., Inc. | 4/38-1/52; eliminated 10/53 |
| Shell Oil Co. | added 10/53; 10/57-1/80; eliminated 1/80 | |
| SCDX | Swift Canadian Co., Ltd. | 4/38-1/52 |
| SCEX | Southern California Edison Co. | added 10/58; 4/61-7/2000 |
| SCFE | South Central Florida R.R., Division of Brandywine Valley R.R. Co. | added 1/91; 1/94; eliminated 1/95; eliminated 4/95 |
| South Central Florida Express, Inc. | added 1/95; added 4/95; 7/2000 | |
| SCFS | Straits Car Ferry Service Corp. | Jan-80 |
| SCGX | Schuler Grain Co. | 1/80; eliminated 4/90 |
| Eades Commodities Co. | added 4/90; 1/94; eliminated 7/2000 | |
| General Electric Rail Services Corp. | added 7/2000; 7/2000 | |
| SCHX | Stauffer Chemical Co., Inc. (Eastern Branch) | 4/38-1/52; eliminated 7/56 |
| Stauffer Chemical Co. (Eastern Branch) | added 7/56; 10/57-1/80 | |
| Stauffer Chemical Co. | eliminated 4/90 | |
| Rhone-Poulenc Basic Chemicals Co. | added 4/90; 1/94; eliminated 10/99 | |
| Rhodia, Inc. | added 10/99; 7/2000 | |
| SCIX | Samuel Cabot Inc. | 4/38-4/70; eliminated 7/70 |
| Skeena Celluose, Inc. | added 10/87; 1/94; eliminated 7/94 | |
| General Electric Railcar Services Corp. | added 7/94; eliminated 4/98; added 4/99; eliminated 1/2000 | |
| General Electric Rail Services Corp. | added 1/2000; 7/2000 | |
| SCJX | Spencer Chemical Co. | 1/52-4/61; eliminated 4/65 |
| Warren Petroleum Co. | added 4/65; 7/65-10/66 | |
| Warren Petroleum Corp. | eliminated 1/70 | |
| Gulf Oil Co.--U.S., Division of Gulf Oil Corp. | added 1/70; 4/70-1/80; eliminated 7/82 | |
| Gulf Refining and Marketing Co., Division of Gulf Oil Corp. | added 7/82 | |
| Chevron U.S.A., Inc. | 1/94; eliminated 4/96 | |
| Chevron Chemical Co. | added 4/96; 7/2000; eliminated 1/2001 | |
| Chevron Phillips Chemical Co. L.P. | added 1/2001 | |
| SCK | South Central Arkansas Ry., Inc. | added 7/82 |
| SCKX | Spring Creek Coal Co. | eliminated 10/86 |
| Northern Coal Transportation Co. | added 10/86; 1/94-7/2000 | |
| SCL | Seaboard Coast Line R.R. Co. | 4/70-1/80; eliminated 1/83 |
| Seaboard System R.R., Inc. | added 1/83; eliminated 7/87 | |
| CSX Transportation, Inc. | added 7/87; 1/94-7/2000 | |
| SCLX | Samuet Cabot, Inc. | Apr-38 |
| Standard Chemical Co., Ltd. | Apr-38 | |
| Standard Chemical, Ltd. | added 7/55; 10/57-1/75 | |
| Stanchem Division, PPG Industries Canada Ltd. | 1/80; eliminated 7/84 | |
| PPG Canada, Inc. | added 7/84; eliminated 10/84 | |
| PPG Canada, Inc., Industrial Chemicals | added 10/84; 1/94; eliminated 1/97 | |
| CanadianOxy Industrial Chemicals Limited Partnership | added 1/97; 7/2000 | |
| SCM | Strouds Creek & Muddlety R.R. | 1/75-1/94 |
| SCMX | Shell Chemical Co. | 4/38-1/52 |
| Shell Chemical Corp. | Oct-57 | |
| Shell Chemical Co., a Division of Shell Oil Co. | 4/61-10/66; eliminated 7/69 | |
| Shell Oil Co. | added 7/69; 4/70-7/2000 | |
| SCNX | Columbian Gasoline Corp. | 4/38-1/52 |
| South Carolina Electric & Gas Co. | added 1/99; 7/2000 | |
| SCOX | The Sco Tank Line, Inc. | Apr-38 |
| Scoular Bishop Grain Co. | added 4/79; 1/80 | |
| The Scoular Co. | 1/94; eliminated 10/99; 7/2000 | |
| SCPX | Shell Chemical Co., a Division of Shell Oil Co. | 7/65-10/66; eliminated 7/69 |
| Shell Oil Co. | added 7/69; 4/70-7/2000 | |
| SCRF | South Carolina Central R.R. Co., Inc. | added 4/88; 1/94-7/2000 |
| SCRX | Santa Clarita Railway d/b/a James Clark & Co. | Jul-00 |
| SCST | Seaboard Transportation Co., a Wholly Owned Subsidiary of the Seaboard Coast Line R.R. Co. | 1/94-7/2000 |
| SCSX | The CIT Group/Capital Finance, Inc. | added 10/98; 7/2000 |
| SCT | Sioux City Terminal Ry. | 1/75-7/2000 |
| SCTR | South Central Tennessee R.R. Co., Inc. | added 10/78; 1/80-1/94; eliminated 10/94 |
| South Central Tennessee R.R. Corp. | added 10/94; 7/2000; eliminated 4/2001 | |
| SCTRR, LLC | added 4/2000 | |
| SCWX | South Carolina Public Service Authority | added 4/79; 1/80-1/94; eliminated 1/99; 7/2000 |
| SCX | The Shasta Water Co. | 4/38-1/52 |
| SCXF | South Central Florida Express, Inc. | added 1/95; added 4/95; 7/2000 |
| SCXY | St. Croix Valley R.R. Co. | added 1/98; 7/2000 |
| SCYX | Farmers Cooperative Association of York, Nebraska | added 4/81; eliminated 7/88 |
| U.S. Rail Services, Inc. | added 7/88; 1/94; eliminated 4/94 | |
| USL Capital Rail Services | added 4/94; eliminated 10/96 | |
| First Union Rail | added 10/96; 7/2000 | |
| SDAE | San Diego and Arizona Eastern Ry. Co. | 4/38-1/75; eliminated 1/80 |
| San Diego and Arizona Eastern Ry. Co., Kyle Santa Rosa, Inc.--Operation-Over | added 1/80; 1/80; eliminated 4/80; eliminated 10/80 | |
| San Diego and Arizona Eastern Transportation Co. | added 10/80 | |
| SDCX | Southern Dyestuff Corp. | 1/52-10/57; eliminated 1/58 |
| Smith-Douglass Co., Inc. | 7/65; eliminated 10/65 | |
| Smith-Douglass, a Division of the Borden Chemical Co. | added 10/65; 10/66; eliminated 10/69 | |
| Smith-Douglass, a Division of Borden Chemical, Borden, Inc. | added 10/69; 4/70; eliminated 1/72 | |
| Borden Chemical, Division of Borden, Inc. | added 1/72; 1/75-1/80 | |
| AMAX Phosphate, Inc. | added 7/81 | |
| AMAX Chemical Corp. | eliminated 1/88 | |
| Consolidated Minerals, Inc., Feed Supplement Division | added 1/88; 1/94-7/2000 | |
| SDEX | Swindell-Dresser Energy Supply Co. | 1/80-7/2000; eliminated 4/2001 |
| Savage-Harrington Energy | added 4/2001 | |
| SDIT | San Diego & Imperial Valley Ry. Co. | added 10/84 |
| SDIX | Smith-Douglass Co., Inc. | 1/52; eliminated 4/57 |
| SDIY | San Diego & Imperial Valley R.R. Co. | eliminated 10/92; 1/94-7/2000 |
| SDPX | South Dakota Soybean Processors, Inc. | added 4/97; eliminated 1/99; added 7/2000; 7/2000 |
| SDRX | Sinclair Refining Co. | 4/38-1/52; eliminated 1/58 |
| Union Tank Car Co. | 10/57; added 1/58; 4/61-4/70; eliminated 7/73 | |
| Central Puget Sound Regional Transit Authority | Jul-00 | |
| SDX | Squire Dingee Co. | 4/38-4/61 |
| SE | Ferrocarrils Unidos del Sureste, S.A. de C.V. | 1/75-1/80 |
| Semo Port R.R., Inc. | added 1/95; 7/2000 | |
| SEAX | Seahorse Fuels, Inc. | added 1/62; 7/65-4/70 |
| SECX | Southern Extract Co. (The Mead Corp.) | Apr-38 |
| South-East Coal Co. | added 1/75; 1/75-1/80; eliminated 7/93; 1/94 | |
| General Electric Railcar Services Corp. | eliminated 1/2000 | |
| General Electric Rail Services Corp. | added 1/2000; 7/2000 | |
| SEFX | North American Rails Leasing Corp. | added 1/99; 7/2000 |
| SEGX | Eades Commodity Co. | added 7/2000; 7/2000 |
| SEI | Southeastern International Corp. | Jul-00 |
| SEIX | Seimax Gas Corp. | added 11/73; 1/75-1/94; eliminated 7/97; 7/2000 |
| SEKR | Southeast Kansas R.R. Co. | added 10/88; 1/94; eliminated 10/96; 7/2000 |
| SEMX | Seminole Electric Cooperative, Inc. | added 1/83; 1/94-7/2000 |
| SEPA | Southeastern Pennsylvania Transporation Authority (passenger commuter operation) | 1/94-7/2000 |
| SEPX | Shell Eastern Petroleum Products (Shell Union Oil Corp.) | Apr-38 |
| SEPX | Southwestern Electric Power Co. | 1/80-7/2000 |
| SEQX | Sequa Chemicals, Inc. | added 4/97; 7/2000 |
| SERA | Sierra R.R. Co. | 1/75-1/80; eliminated 1/88; eliminated 10/91; 1/94-7/2000 |
| SERX | Service Tank Car Co. | Apr-38 |
| Shippers' Car Line Corp. (Service Tank Car Co.) | Jan-52 | |
| Shippers' Car Line Corp. | eliminated 7/56 | |
| Shippers' Car Line Division of ACF Industries, Inc. | added 7/56; 10/57-1/80; eliminated 4/88 | |
| ACF Industries, Inc. | added 4/88; 1/94-7/2000 | |
| SESX | Sessions Co., Inc. | 1/52-4/61 |
| SESX | B.C. Hydro | added 1/90; eliminated 1/94; 7/2000 |
| SFAL | SF&L Ry., Inc. | 1/94-7/2000 |
| SFB | San Francisco Belt | Jan-94 |
| SFCX | Sheffield Farms Co., Inc. | Apr-38 |
| Southern Fertilizer and Chemical Co. | Oct-57 | |
| SFDX | Southern Fruit Distributors, Inc. | 1/52-4/61; eliminated 1/65 |
| SFIX | System Fuels, Inc. | 1/80; added 4/80; 1/94; eliminated 4/98 |
| HELM Financial Corp. | added 4/98; 7/2000 | |
| SFLC | Atchison, Topeka & Santa Fe Ry. Co. | added 7/77; 1/80-1/94; eliminated 7/97 |
| Burlington Northern Santa Fe Ry. Co. | added 7/97; 7/2000 | |
| SFLR | The Shore Fast Line, Inc. | eliminated 7/92; 1/94-7/2000 |
| SFPP | Spruce Fall Power & Paper | 1/75-1/80 |
| SFQ | The Burlington Northern Santa Fe Ry. Co. | Jul-00 |
| SFR | Southern Freight Logistics, LLC d/b/a Southern Freight R.R. | Jul-00 |
| SFRA | Atchison, Topeka & Santa Fe Ry. | 7/65-1/75 |
| SFRB | Atchison, Topeka & Santa Fe Ry. | 10/57-1/80; eliminated 1/86 |
| SFRC | Atchison, Topeka & Santa Fe Ry. Co. | 4/61-1/94; eliminated 7/97 |
| Burlington Northern Santa Fe R.R. Co. | added 7/97 | |
| SFRD | Atchison, Topeka & Santa Fe Ry. Co. | 4/38-1/80; eliminated 7/80 |
| SFRE | Atchison, Topeka & Santa Fe Ry. | 7/65-1/80; eliminated 1/86 |
| SFRF | Atchison, Topeka & Santa Fe Ry. | 10/66-1/75 |
| SFRM | Atchison, Topeka & Santa Fe Ry. | 7/65-1/75 |
| SFRP | Atchison, Topeka & Santa Fe Ry. | 7/65-1/80; eliminated 1/81 |
| SFRX | Southern Foundry Supply, Inc. | added 10/96; eliminated 4/2000; 7/2000 |
| Philip Metals, Inc. | added 4/2001 | |
| SFS | Santa Fe Southern Ry., Inc. | added 7/92; eliminated 1/94; eliminated 1/98; 7/2000 |
| SFSX | San Francisco Transportation Services Co. | added 1/78; eliminated 10/78 |
| San Francisco Transportation Services Co., Inc. | added 10/78; 1/80; eliminated 10/83; 1/94-7/2000 | |
| SFT | Springfield Terminal Ry. (Illinois) | 4/38-1/52 |
| SFTX | Suburban Fuel Tank Car Co. | 4/61-1/75; eliminated 1/79 |
| Continental Tank Car Corp. | added 1/79; 1/80-7/2000 | |
| SFX | Southern Fertilizer & Chemical Co. | Apr-38 |
| Stokely Foods, Inc. | Jan-52 | |
| SGAX | SGA Leasing Co. | 1/94-7/2000 |
| SGCX | Sungas Corp. of Florida | added 1/74; 1/75-7/2000 |
| SGIX | Werner's, Inc. | added 1/62; 7/65-1/80; eliminated 4/80 |
| LPG Transportation, Inc. | added 4/80; eliminated 1/91 | |
| Suburban Gas, Inc. | added 1/91; eliminated 4/91 | |
| Vision Energy Minnesota, Inc. | added 4/91; eliminated 10/91; 1/94-7/2000 | |
| SGLR | Seminole Gulf Ry. L.P. | added 4/88; 1/94-7/2000 |
| SGRX | Skip Gibbs | Jul-00 |
| SGSX | Sure-Grow Solutions, Inc. | added 10/89; 1/94; eliminated 10/94 |
| SGSX | Terra International, Inc. | Jul-00 |
| SGVY | Saginaw Valley Ry. Co., Inc. | 1/94-7/2000 |
| SH | Steelton & Highspire R.R. Co. | 1/75; added 1/80; 1/80-1/94; eliminated 10/99; 7/2000 |
| SHLX | Procor Ltd. | added 1/98; 7/2000 |
| SHPX | Shippers' Car Line Corp. | 4/38-1/52; eliminated 7/56 |
| Shippers' Car Line Division of ACF Industries, Inc. | added 7/56; 10/57-1/80; eliminated 4/88 | |
| ACF Industries, Inc. | eliminated 4/88; eliminated 10/93; 1/94; added 7/97; 7/2000 | |
| SI | Spokane International R.R. Co. | 1/75-1/80; added 1/88 |
| Union Pacific R.R. Co. | added 4/88; 1/94; eliminated 4/94; 7/2000 | |
| SICX | Sloss Industries Corp. | added 7/88; 1/94-7/2000 |
| SIEX | Southern Iron & Equipment Co. | added 10/70 |
| Southern Iron & Equipment Co., Division U.S. Railway Manufacturing Co. | 1/75; eliminated 7/77 | |
| Southern Iron & Equipment Co., Division Evans Transportation Co. | added 7/77; eliminated 7/79 | |
| United States Leasing Co. | added 7/79; 1/80 | |
| United States Railway Leasing Co. | eliminated 10/80 | |
| Southeastern Industrial Enterprises, Inc. | added 4/95; 7/2000 | |
| SIGX | Southern Indiana Gas and Electric Co. | added 4/79; 1/80-7/2000 |
| SILX | The Silurian Oil Co. (W.C. McBride, Inc.) | Apr-38 |
| Jeffersonville Silgas, Inc. | 1/52-10/66; eliminated 10/69 | |
| SIMX | North American Car Corp. | added 7/64; 7/65-4/70 |
| Sierra Bag Co. | added 1/83; eliminated 1/89 | |
| SIND | Southern Indiana Ry., Inc. | 1/75-1/80; eliminated 7/89; 1/94-7/2000 |
| SIPX | Arrendadora Sipco, S.A. de C.V. | added 7/94; 7/2000 |
| SIR | Staten Island Rapid Transit Ry., Co. | 4/38-4/70 |
| SIRC | Staten Island R.R. Corp. | 1/75-1/80 |
| SIRR | Southern Industrial R.R., Inc. | 1/75-7/2000 |
| SIRX | Southern Illinois Railcar Co. | added 1/91; 1/94-7/2000 |
| SIRY | Staten Island Ry. Corp. (transferred to New York, Susquehanna and Western Ry. Corp.) | eliminated 10/88 |
| Staten Island Ry. Corp. | eliminated 4/92; 1/94 | |
| SITX | Sherritt International Corp. | added 4/97; 7/2000 |
| SJB | St. Joseph Belt Ry. Co. | 4/38-1/75 |
| SJEX | SJEX, Inc. | added 7/86; eliminated 1/90; 1/94-7/2000 |
| SJGI | St. Joseph & Grand Island Ry. | 4/38-1/52 |
| SJ&L | St. Johnsbury & Lake Champlain R.R. Co. | Apr-38 |
| SJL | St. Johnsbury & Lamoille County R.R. | 4/61-4/70; eliminated 11/73; added 4/74; 1/75; eliminated 7/77 |
| Vermont Northern R.R. Co. | added 1/78; eliminated 4/78 | |
| SJLX | St. Joseph Lead Co. | 4/61-4/70; eliminated 10/70 (reporting marks changed to SJMX) |
| SJMX | St. Joe Minerals Corp. (name changed to Zinc Corp. of America, reporting marks to ZCAX) | added 10/70; 1/75-1/80; eliminated 10/88 |
| SJNX | Mobay Corp. | 1/94-7/2000 |
| SJRT | St. Johns River Terminal | 1/75-7/2000 |
| SJRX | Jacksonville Electric Authority | added 10/86; 1/94; eliminated 1/95; 7/2000 |
| SJT | St. Joseph Terminal R.R. Co. | 1/75-1/80 |
| SJVR | San Joaquin Valley R.R. Co. | added 4/92; 1/94-7/2000 |
| SJWX | Transportation Management, Inc. | 1/75; added 4/75 |
| Missouri Valley Walnut Co. | 1/80; eliminated 1/82 | |
| SKCX | Sinclair-Koppers Co. | added 1/68; 4/70 |
| ARCO Polymers, Inc. | 1/75-1/80; eliminated 10/82 | |
| ARCO Chemical Co. | added 10/82; 1/94-7/2000 | |
| SKGX | Sibley Railcar & Pats, Inc. | Jul-00 |
| SKNX | The Saskatchewan Grain Car Corp. | added 1/81; 1/94-7/2000 |
| SKOL | South Kansas & Oklahoma R.R., Inc. | added 4/92; 1/94; eliminated 1/97; added 7/98; 7/2000 |
| SKPR | Southern Kent & Pacific R.R. Co. | 1/94-7/2000 |
| SKPX | The Saskatchewan Grain Car Corp. | added 1/81; 1/94-7/2000 |
| SKRX | Schuylkill Railcar L.P. | added 10/98; 7/2000; eliminated 7/2000 |
| SKX | Spencer Kellogg & Sons, Inc. | Apr-38 |
| S&L | Sydney & Louisburg Ry. | 4/38-4/61 |
| Cumberland Ry. | Jul-65 | |
| SL | Sugar Land Ry. | 4/38-1/52 |
| Salt Lake City Southern R.R. Co., Inc. | 1/94-7/2000 | |
| SLAL | South Plains Lamesa R.R., Ltd. | Jul-00 |
| SLAW | St. Lawrence R.R., Division of National Railway Utilization Corp. | Jan-80 |
| St. Lawrence R.R. | eliminated 7/90 | |
| SLAX | St. Lawrence Starch Co. Ltd. | 4/38-1/80; eliminated 10/87 |
| SLC | San Luis Central R.R. | Jan-52 |
| The San Luis Central R.R. Co. | 1/75-7/2000 | |
| SLEX | Short Line Enterprises, Ltd. | 1/94-7/2000 |
| SLGG | Sidney & Lowe R.R., Inc. | added 10/83; eliminated 4/89; eliminated 4/91; added 7/92; 1/94; eliminated 4/97 |
| Progress Rail Services Corp. d/b/a Sidney & Lowe R.R., Inc. | added 4/97; 7/2000 | |
| SLGW | Salt Lake, Garfield and Western Ry. Co. | 1/75-1/80; eliminated 4/89; 1/94-7/2000 |
| SL&H | St. Louis & Hannibal R.R. Co. | Apr-38 |
| SLH | St. Louis & Hannibal Ry. | Jan-52 |
| SL&L | Salt Lake, Garfield & Western Ry. Co. | Apr-38 |
| SLOF | St. Louis and O'Fallon Ry. | 4/38-1/52 |
| SLOX | Selox, Inc. | eliminated 7/92 |
| SLQ | St. Lawrence & Atlantic R.R. (Quebec) Inc. | Jul-00 |
| SLR | St. Lawrence & Atlantic R.R. Co. | added 10/89; 1/94-7/2000 |
| SLRR | St. Lawrence & Raquette River R.R. | added 7/90; eliminated 1/94 |
| SLRS | SMS Rail Service, Inc. | Jul-00 |
| SLRX | St. Louis Refrigerator Car Co. | 4/38-4/70; eliminated 4/73; added 1/74; 1/75; eliminated 1/75; 1/80; eliminated 4/81 |
| SLS | Sea-Land Service, Inc. | Jan-75 |
| SLSF | St. Louis-San Francisco Ry. Co. | 4/38-1/80; eliminated 1/81; 7/2000 |
| Burlington Northern Inc. | added 1/81; eliminated 7/81 | |
| Burlington Northern R.R. Co. | added 7/81; 1/94 | |
| SLSX | Swift Live Stock Express (General American Transportation Corp.) | Apr-38 |
| General American Transportation Corp. | 1/52-7/65 | |
| Swift Live Stock Express (General American Transportation Corp.) | 10/66; eliminated 1/70 | |
| SLTX | Slade Transport, Inc. | added 7/74; 1/75-1/80; eliminated 4/87 |
| SLU | Salt Lake & Utah R.R. | 4/38-1/52 |
| SLVX | Silver Enterprises | Jul-00 |
| SLWC | Stillwater Central R.R. Co., Inc. | Jul-00 |
| SM | St. Marys R.R. Co. | 1/75; eliminated 1/79; 1/80-7/2000 |
| SMA | San Manuel Arizona R.R. Co. | 1/75-7/2000 |
| SMAX | Siemens-Allis, Inc. | added 4/85; eliminated 4/86 |
| SMAX | Siemens | added 4/86; eliminated 10/88 |
| SMCX | The Altus Co. | added 1/62 |
| Standard Milling Co. | 7/65-4/70; eliminated 4/72 | |
| San Miguel Electric Cooperative, Inc. | added 10/81; 1/94-7/2000 | |
| SMEX | South Mississippi Electric Power Association | added 1/78; 1/80-7/2000 |
| SMIX | Schreiber Mills, Inc. | added 7/59; 4/61-1/75; eliminated 7/76 |
| Structural Metals, Inc. | added 1/86; 1/94-7/2000 | |
| SMMX | St. Marys Cement Co. | 1/94-7/2000 |
| SMNR | Southern Manitoba Ry., Inc. | Jul-00 |
| SMNX | Solvay Minerals, Inc. | Jul-00 |
| SMOX | Standard Molasses Co. | 1/52; eliminated 10/57 |
| SMPX | Shell-Mex Oil Co. of Cuba, Ltd. (Cia Petrolera Shell--Mex de Cuba, S.A.) | Apr-38 |
| Commercial Metals Co. | added 1/97; added 4/97; 7/2000 | |
| SMRR | Sisseton Milbank R.R. Inc. | added 10/89; 1/94-7/2000 |
| SMRX | Sampierre Chemical Corp. | added 10/60; 4/61 |
| Atlanta Chapter--National Railway Historical Society, Inc. | Jul-00 | |
| SMSX | S. Morgan Smith Co. | 4/38-10/57 |
| SMV | Santa Maria Valley R.R. Co. | 1/75-7/2000; eliminated 10/2000 |
| SMX | Staley Milling Co. | Jan-52 |
| Socony Mobil Oil Co., Inc. | 10/57-4/61 | |
| SN | Sacramento Northern Ry. | 10/57-1/80; eliminated 10/87 |
| Union Pacific R.R. Co. | added 10/87; eliminated 4/88 | |
| SNAX | Sociedad Nacional de Productores de Alcohol | 1/52-1/75 |
| SNBL | Sioux City & New Orleans Barge Line | 1/75-7/2000 |
| SNCO | Seaport Navigation | 1/75-1/80 |
| SNCT | Seattle & North Coast R.R. Co. | added 4/80; eliminated 1/89 |
| SNFX | Shell Chemical Co., a Division of Shell Oil Co. | added 10/66; 10/66; eliminated 7/69 |
| Shell Oil Co. | added 7/69; 4/70-1/80; eliminated 1/83 | |
| IND/AG Chemicals, Inc. | added 1/83; 1/94-7/2000 | |
| SNGX | Southeastern Natural Gas Corp. | added 4/62 |
| Tropigas Inc. of Florida | 7/65; eliminated 1/66 | |
| SNHX |