| (P&OV) Pittsburgh & Ohio Valley Ry. Co. | POV | Apr-70 | |
| (PA&M) Pittsburgh, Allegheny & McKees Rocks R.R. Co. | PAM | 4/70; eliminated 4/89 | |
| (PH&D) Port Huron and Detroit R.R. Co. | PHD | Apr-70 | |
| P.D. Transportation Co. | PDTX | added 1/74; 1/75; eliminated 10/78 | |
| P.J. O'Donnell & Sons | PJOX | 1/52-7/65; eliminated 10/66 | |
| P4 Production, L.L.C. | MSPX | added 1/98; 7/2000 | |
| Pacer International d/b/a Pace Stacktrain | PASX | added 4/2000; 7/2000 | |
| Pacer Rail Services, LLC | PCRX | Jul-00 | |
| Pacific Car and Foundry Co. | PCFX | added 7/82 | |
| Pacific Coast R.R. Co. | PC | 4/38-10/66 | |
| Pacific Electric Ry. | PE | 1/52-7/65 | |
| Pacific Fruit Express Co. | PFE | 4/38-1/80; eliminated 4/89 | |
| PFF | added 1/62; 7/65-1/75; eliminated 1/75 | ||
| Pacific Great Eastern Ry. Co. | PGE | 4/38-10/66 | |
| Pacific Harbour Line, Inc. | PHL | added 4/98; 7/2000 | |
| Pacific Lumber Co. | TPLX | 1/52; eliminated 7/55 | |
| Pacific Metal, Ltd. | PMGX | Jul-00 | |
| Pacific Northwest Salvage, Inc. | PNWX | added 4/81; eliminated 10/89 | |
| Pacific Nuclear Systems, Inc. | PNSX | added 1/88; 1/94; eliminated 4/95 | |
| Pacific Petrochemicals, Inc. | PPIX | added 10/65; 10/66; eliminated 7/68 | |
| PPIX | eliminated 4/70 | ||
| Pacific Portland Cement Co. | PPSX | Apr-38 | |
| Pacific Rail Dismantling Services, Inc. | PRDX | 1/94-7/2000 | |
| Pacific Rail Leasing Corp. | PRAX | added 7/91; 1/94; eliminated 7/96 | |
| Pacific States Railcar Co. | PSBX | added 1/74; 1/75-1/94; eliminated 4/98 | |
| Pacific Supply Cooperative | PACX | added 10/74; 1/75; eliminated 1/78 | |
| Pacific Tank Line | PATX | Apr-38 | |
| Pacific Vegetable Oil Corp. | PVOX | 1/52-4/61; eliminated 4/62 | |
| Pacific Western Resin Co. | PWRX | 1/94-7/2000 | |
| PacifiCorp Electric Operations & Idaho Power Co.-Jim Bridger Project | JBPX | added 4/91; eliminated 7/92; 1/94-7/2000 | |
| Packaging Corp. of America | TMAX | added 10/91; 1/94; eliminated 7/98 | |
| Packers Car Line Co. | PCX | added 4/57; 10/57-4/70 | |
| Packers Cold Storage, Inc. | PCSX | added 7/79; 1/80; eliminated 7/80 | |
| Paducah & Illinois R.R. | PI | 1/75-7/2000 | |
| Paducah & Louisville Ry., Inc. | PAL | added 10/86; 1/94-7/2000 | |
| Paktank Gulfcoast, Inc. | TECX | added 1/77 | |
| Palomar Oil & Refining Corp. | PRX | 1/52-4/61 | |
| Palouse River & Coulee City R.R. Inc. | PCC | Jul-00 | |
| Pan American Liquids Service Co., Inc. | PALX | eliminated 4/78 | |
| Pan American Ry. Co. | PARX | added 4/75; 1/80-7/2000 | |
| Pan-Am Southern Corp. | PASX | 1/52; eliminated 4/57 | |
| Panama Gypsum Co. | YSMX | added 1/62; 7/65-1/75; eliminated 4/76 | |
| Pandrol Jackson, Inc. | RMSX | Jan-94 | |
| Panhandle Northern R.R. Co. | PNR | Jul-00 | |
| Panoma Corp. | PANX | Jan-52 | |
| Panther Valley R.R. Corp. | PVAL | added 4/84; eliminated 10/87; eliminated 4/90 | |
| Paper Makers Chemical Corp., Ltd. | PMCX | Apr-38 | |
| Pargas Tank Cars, Inc. | POTX | added 10/65; 10/66; eliminated 1/68 | |
| Pargas, Inc. | POTX | added 1/68; 4/70-1/80; eliminated 1/86 | |
| Paris & Mt. Pleasant R.R. | PMP | 4/38-1/52 | |
| Parker Brothers & Co., Inc. | PBCX | added 1/74; 1/75; eliminated 4/76 | |
| Parks Furniture Co., Inc. | PFRX | added 4/85; eliminated 1/93 | |
| Parks Propane & Appliance Inc. | PFRX | added 1/93; 1/94; eliminated 4/2000; 7/2000 | |
| Parr Terminal R.R. | PRT | 1/75-1/94; eliminated 7/97; 7/2000 | |
| Pasbro Holding Co. | MWPX | added 7/69; 4/70-1/75; eliminated 4/78 | |
| Patapsco & Back Rivers R.R. Co. | PBR | 1/52-1/94; eliminated 10/99; 7/2000 | |
| Pavers Supply Co. | PSUX | added 4/82; eliminated 10/87 | |
| Paxon Polymer Co., L.P. | EPAX | added 7/96 | |
| Paxon Polymer Co., L.P. II an Exxon Chemical Affiliate | EPAX | eliminated 7/2000 | |
| PCS Phosphate Co., Inc. | PPAX | added 4/99; 7/2000 | |
| PPHX | added 10/97; 7/2000 | ||
| PPNX | added 4/99; 7/2000 | ||
| PPTX | added 10/97; 7/2000 | ||
| TGAX | added 10/95; 7/2000 | ||
| TGIX | added 10/95; 7/2000 | ||
| WAGX | added 4/96; 7/2000 | ||
| Peabody Coal Co. | PCCX | added 4/68; eliminated 10/68; 4/70; added 1/71; eliminated 4/72; 1/75-1/94 | |
| Peabody Coal Co. (captive service) | PCCX | added 10/57; 10/57-10/66 | |
| Peabody Coal Co. (captive service) | PCCX | Jul-00 | |
| Peabody Short Line R.R. | PSL | Apr-61 | |
| Pearl Packing Co. (National Car Co.) | PPIX | Apr-38 | |
| Pearl River Valley R.R. Co. | PRV | 1/75-1/80; eliminated 10/86; 1/94-7/2000 | |
| Peavey Co. | PVFX | added 4/82; eliminated 1/83 | |
| PVGX | 1/80; eliminated 1/83 | ||
| Peck Iron & Metal Co., Inc. | RAYX | 7/65-10/66; eliminated 10/67 | |
| Pee Dee River R.R. Co. | PDRR | Jan-94 | |
| Pee Dee River R.R. Corp. | PDRR | added 1/95; 7/2000 | |
| Pekin Energy Co. | PECX | added 1/83; eliminated 7/84 | |
| Pend Oreille Valley R.R. | POVA | added 1/85; eliminated 7/86; 1/94-7/2000 | |
| Pend Oreille Valley R.R., Inc. | POVA | added 1/80; 1/80; eliminated 1/85 | |
| Penford Products Co. | PENX | added 10/95; 7/2000 | |
| Penick & Ford Tank Line (General American Transportation Corp.) | PFTX | Apr-38 | |
| Peninsula Terminal Co. | PT | 1/75; added 7/78; 1/80; added 10/86; 1/94-7/2000 | |
| Penn Central Transportation Co. | PC | Jan-75 | |
| PCA | Jan-75 | ||
| PCB | Jan-75 | ||
| PRR | 4/70-1/75 | ||
| BA | Jan-75 | ||
| BWC | Jan-75 | ||
| NH | Jan-75 | ||
| NYC | Jan-75 | ||
| TOC | 4/70-1/75 | ||
| Penn Central Transportation Co. (Canada Southern Ry.) | CASO | Jan-75 | |
| Penn Central Transportation Co., Robert W. Blanchette, Richard C. Bond and John H. McArthur, Trustees | PAE | eliminated 4/76 | |
| PC | eliminated 4/76 | ||
| PCA | eliminated 4/76 | ||
| PCB | eliminated 4/76 | ||
| P&E | eliminated 4/76 | ||
| PRR | eliminated 4/76 | ||
| BA | eliminated 4/76 | ||
| BWC | eliminated 4/76 | ||
| CASO | eliminated 4/76 | ||
| NH | eliminated 4/76 | ||
| NYC | eliminated 4/76 | ||
| TOC | eliminated 4/76 | ||
| Penn Eastern Rail Lines Inc. | BITY | added 4/98; 7/2000 | |
| CHTS | added 4/98; 7/2000 | ||
| LANO | added 4/98; 7/2000 | ||
| PRL | added 4/98; 7/2000 | ||
| Penn Jersey Rail Lines Inc. | PJRL | Jul-00 | |
| Penn-Dixie Cement Corp. | PDSX | 1/52-4/70 | |
| PDSX | eliminated 10/81 | ||
| Penn-Dixie Industries, Inc. | PDSX | 1/75-1/80 | |
| Penn-Dixie Leasing Corp. | PDQX | added 1/69; 4/70 | |
| Pennsalt Carriers Corp. | TELX | added 1/69; 4/70; eliminated 1/75 | |
| Pennsalt Chemicals Corp. | TELX | added 10/60; 4/61-10/66; eliminated 1/69 | |
| Pennsalt of Washington Division, Pennsalt Chemicals Corp. | TELX | added 10/57; 10/57; eliminated 10/60 | |
| Pennsylvania and Atlantic R.R. Co. | PAUT | Jan-75 | |
| Pennsylvania Lines LLC | PRRX | Jul-00 | |
| Pennsylvania Oil Products Refining Co. | POPX | Apr-38 | |
| Pennsylvania Power & Light Co. | PPLX | 7/65-7/2000 | |
| Pennsylvania Pullmans Inc. | PAPX | Jul-00 | |
| Pennsylvania R.R. | PRR | 4/38-10/66 | |
| BWC | 7/65-10/66 | ||
| Pennsylvania Salt Manufacturing Co. of Washington | TELX | eliminated 10/57 | |
| Pennsylvania Salt Mfg. Co. | PSMX | 4/38-1/52 | |
| Pennsylvania Sugar Co. | PSUX | Apr-38 | |
| Pennsylvania Tank Line (Pennsylvania-Conley Tank Line, a Division of General American Transportation Corp.) | PTX | Apr-38 | |
| Pennsylvania-Conley Tank Line, a Division of General American Transportation Corp. | PTX | Apr-38 | |
| Pennsylvania-Dixie Cement Corp. | PDSX | Apr-38 | |
| Pennsylvania-Reading Seashore Lines | PRSL | Jan-75 | |
| Pennwalt Carriers Corp. | TELX | added 1/75; 1/75-1/80; eliminated 1/93 | |
| Pennzoil Co. | DVLX | added 4/92; 1/94; eliminated 4/96 | |
| Pennzoil Sulphur Co. | DVLX | added 4/85; eliminated 4/92 | |
| Pennzoil United, Inc. | ERCX | eliminated 4/73 | |
| Peoples Gas By-Products Corp. | PGBX | Apr-38 | |
| Peoples Gas Systems, Inc. | PGCX | 1/94-7/2000; eliminated 4/2001 | |
| Peoples Transportation Co. | PTCX | 7/65; eliminated 7/66 | |
| Peoria & Eastern Ry. | PAE | Jan-75 | |
| PE | Jan-75 | ||
| Peoria & Pekin Union Ry. | P&PU | 4/38-4/70 | |
| Peoria & Pekin Union Ry. Co. | PPU | 7/65-7/2000 | |
| Peoria Packing Co. | PPAX | Apr-38 | |
| Peoria Terminal Co. | PTC | 1/75-1/80 | |
| Peoria Terminal Co. (Chicago, Rock Island & Pacific Ry.) | PT | Apr-38 | |
| Pepin Pickling Co. | PPPX | 4/38-1/52 | |
| Peppers Refining Co. | PEPX | 4/38-1/52 | |
| Perdue Transportation, Inc. | PFMX | added 1/98; 7/2000 | |
| Perfect Packed Products Co., Inc. | PPCX | 1/52-10/57; eliminated 7/59 | |
| Perkins Motor Transport, Inc. | NLPX | Jul-00 | |
| Permanente Cement Co. | OPCX | added 7/59; 4/61 | |
| Petaluma & Santa Rosa R.R. | P&SR | 4/38-4/70 | |
| Petaluma & Santa Rosa R.R. Co. | PSR | 7/65-10/66 & 1/75-1/80; eliminated 10/84 | |
| Petco Corp. | PETX | eliminated 10/53 | |
| Petco Corp., Great Lakes Refining Division | PETX | Jan-52 | |
| Peter Kiewitt Sons' Co. | TMRX | 1/80; eliminated 7/81 | |
| Peterson Manufacturing Co. | LAFX | Apr-38 | |
| Peterson Manufacturing Co., Inc. | PMCX | 1/52-10/57; eliminated 10/59 | |
| Petro-Chem Marketing Co. | PCMX | added 7/68; 4/70-1/80; eliminated 4/92 | |
| PCMX | added 1/65; 7/65-10/66; eliminated 7/68 | ||
| Petrolane Gas Service Limited Partnership | PYFX | added 7/87; eliminated 7/90 | |
| Petrolane Gas Service Ltd. Partnership | PGRX | added 7/87; 1/94; eliminated 10/95 | |
| TRPX | 1/94; eliminated 10/95 | ||
| Petrolane Gas Service, Inc. | PGRX | 7/65-1/80; eliminated 7/87 | |
| PYFX | added 1/85; eliminated 7/87 | ||
| Petroleos Mexicanos | PMEX | 1/52-1/80; eliminated 10/90; 1/94 | |
| Petroleum Fuels Co. | RWBX | Jan-94 | |
| Petroleum Gas Co. | PEGX | added 10/60; 4/61-10/66; eliminated 1/69 | |
| Petroleum Products, Inc. | BRKX | added 7/88; eliminated 10/89 | |
| Petrolite Corp. | PTRX | added 4/84; 1/94-7/2000 | |
| Petrolite Corp., Bareco Division | PTRX | added 10/65; 10/66-1/80; eliminated 4/84 | |
| Petrolite Corp., Ltd., Tretolite Co. Division | TOLX | Jan-52 | |
| Petromax Chemical Exchange, Inc. | PCEX | added 7/80; eliminated 1/81 | |
| Petrosol International, Inc. | PTSX | 1/94-7/2000 | |
| Petro-Tex Chemical Corp. | PTCX | added 1/75; 1/75-1/80; eliminated 1/85 | |
| Peyton Packing Co. (Mather Stock Car Co.) | PPCX | Apr-38 | |
| Phelps Dodge Corp. | PDOX | Apr-38 | |
| PHDX | added 1/60; 4/61-1/75; eliminated 10/78 | ||
| Philadelphia & Norfolk Steamship | PNS | 1/75-7/2000 | |
| Philadelphia Quartz Co. | PQCX | added 1/71; 1/75; eliminated 4/78 | |
| PQX | 4/38-1/75; eliminated 4/78 | ||
| Philadelphia Quartz Co. of California, Ltd. | PQCX | 4/38-4/70; eliminated 1/71 | |
| Philadelphia Suburban Transportation | PST | 1/75-1/80 | |
| Philadelphia, Bethlehem and New England R.R. Co. | PBNE | 4/38-1/94; eliminated 10/99; 7/2000 | |
| Philip Metals, Inc. | KNOX | added 4/2001 | |
| LUBX | added 4/2001 | ||
| SFRX | added 4/2001 | ||
| PMOX | Jul-00 | ||
| Phillips 66 Co., a Subsidiary of Phillips Petroleum Co. | PSPX | added 7/86; 1/94; eliminated 10/95 | |
| Phillips Petroleum Co. | PPRX | added 1/2001 | |
| PSPX | 4/38-1/80; eliminated 7/86 | ||
| PSPX | added 10/95; 7/2000 | ||
| Phosphate Products Division (Virginia-Carolina Chemical Corp., Phosphate Products Division) | PHPX | Apr-38 | |
| PIC Trans, Inc. | PLRX | Jul-00 | |
| Pickens R.R. Co./Honea Path Division | PKHP | eliminated 1/95 | |
| Pierce & Stevens Chemical Corp. | PSX | eliminated 7/56 | |
| Pierce & Stevens, Inc. | PSX | 4/38-1/52 | |
| Pifer Tank Car Co. | PIFX | added 10/87; 1/94-7/2000 | |
| Pigeon River R.R. Co. | PGRV | added 1/86; eliminated 7/90; 1/94-7/2000 | |
| Piggy-Back Inc. | GPBX | eliminated 1/60 | |
| Piggy-Bank Inc., subsidiary of General American Transportation Corp. | GPBX | added 10/58 | |
| Pine Belt Southern R.R. Co., Inc. | PBRR | Jul-00 | |
| Pinsly R.R. Co. | AKMD | eliminated 7/95 | |
| AKMD | added 7/96 | ||
| FCEN | eliminated 4/97 | ||
| GRN | eliminated 4/97 | ||
| Pinto Valley Copper Corp. | PVCX | eliminated 4/93 | |
| Pioneer Cement Co. of Texas | PCTX | 1/94-7/2000 | |
| Pioneer Chlor Alkali Co., Inc. | PCAX | added 1/91; 1/94; eliminated 7/94; added 10/96; 7/2000; eliminated 4/2001 | |
| Pioneer Equipment Co. | PECX | Jan-52 | |
| Pioneer Industrial Ry. Co. | PRY | Jul-00 | |
| Pioneer Iron & Metal Co. | PIOX | added 4/71; 1/75; eliminated 7/79 | |
| Pioneer Oil & Refining Co. | PNRX | Apr-38 | |
| Pioneer Pipe & Supply Co., Inc. | PPSX | Jul-00 | |
| Pioneer Products Co. | PPX | Jan-52 | |
| Pioneer R.R. Co., Inc./West Jersey R.R. Division | PWJ | added 1/89; eliminated 4/91; 1/94 | |
| Pioneer Railroad Equipment Co. Ltd. | PREX | added 7/94; eliminated 4/97; 7/2000 | |
| Pioneer Valley R.R. Co., Inc. | PVRR | added 10/82; 1/94-7/2000 | |
| Pittman Moore, Inc. | PMIX | added 1/94; 7/2000 | |
| Pittsburg & Shawmut R.R., Inc. | PSR | added 7/96; 7/2000 | |
| Pittsburg County Ry. | PBC | 4/38-1/52 | |
| Pittsburgh & Ohio Central Rd. (was PIR) | POHC | added 4/2001 | |
| Pittsburgh & Ohio Valley Ry. | P&OV | 4/38-10/66 | |
| Pittsburgh & Ohio Valley Ry. Co. | POV | 1/75-1/94; eliminated 1/96; 7/2000 | |
| Pittsburgh & West Virginia Ry. | PW&V | 4/38-7/65 | |
| Pittsburgh & West Virginia Ry. (Norfolk and Western Ry.) | PW&V | Apr-70 | |
| Pittsburgh Coal Carbonization Co. | PCX | Apr-38 | |
| Pittsburgh Crucible Steel Co. | PCSX | Apr-38 | |
| Pittsburgh Industrial R.R., Inc. (to POHC) | PIR | added 4/97; 7/2000; eliminated 4/2001 | |
| Pittsburgh Plate Glass Co. | PPGX | added 4/61; 4/61-10/66; eliminated 4/68 | |
| SACX | added 4/61; 4/61-10/66; eliminated 4/68 | ||
| Pittsburgh, Allegheny & McKees Rocks R.R. | PA&M | 4/38-10/66 | |
| Pittsburgh, Allegheny & McKees Rocks R.R. Co. | PAM | 1/75-1/94; eliminated 1/95; 7/2000 | |
| Pittsburgh, Chartiers & Youghiogheny Ry. Co. | PCY | 1/75-1/94; eliminated 7/97; 7/2000 | |
| Pittsburgh, Lisbon & Western R.R. | PLW | 4/38-1/52 | |
| Pittsburgh, McKeesport & Youghiogheny | PMKY | 1/75-1/80 | |
| Pivotal Enterprises Corp. | PIVX | Jul-00 | |
| PL&W R.R., Inc. | PLW | added 10/93; added 1/94; eliminated 1/96; 7/2000 | |
| Plainview Terminal Co. | PTC | added 1/96; eliminated 4/97; 7/2000 | |
| Planta Almacenadora de Gas, S.A. | PAGX | 10/57-10/66; eliminated 4/69 | |
| Plasser American Corp. | PACX | 1/94-7/2000 | |
| Plastics and Coal Chemicals Division, Allied Chemical Corp. | PLCX | added 10/58; eliminated 4/61 | |
| Plastics Division, Allied Chemical Corp. | PLCX | added 4/61; 4/61; eliminated 7/64 | |
| Plateau Mining Co. | PMCX | added 7/79; 1/80; eliminated 4/87; 1/94 | |
| Platte River Power Authority | RAWX | added 4/84; eliminated 4/90; 1/94-7/2000 | |
| PLEX Division of PLM, Inc. | PLEX | 1/80; eliminated 10/81 | |
| PLM Financial Services, Inc. | PLMX | added 7/84; eliminated 7/89 | |
| PLM International, Inc. | PCSX | added 4/91; 1/94-7/2000 | |
| PLEX | added 7/90; 1/94-7/2000 | ||
| PLMX | added 7/89; 1/94-7/2000 | ||
| CITX | added 4/91; 1/94-7/2000 | ||
| CTEX | added 4/91; 1/94-7/2000 | ||
| DCFX | added 4/91; 1/94-7/2000 | ||
| DCTX | added 4/91; 1/94-7/2000 | ||
| HOMX | added 1/97; 7/2000 | ||
| KCMX | added 4/91; 1/94 | ||
| NCTX | added 4/91; 1/94-7/2000 | ||
| VCSX | added 10/99; 7/2000 | ||
| PLM Railcar Maintenance Co. | MCHX | added 4/85; eliminated 10/89 | |
| PLM Railcar Management Services Canada Limited | CITX | added 1/87; eliminated 4/91 | |
| PLM Railcar Management Services Canada Ltd. | DCFX | added 1/90; eliminated 4/91 | |
| DCTX | added 1/87; eliminated 4/91 | ||
| NCTX | eliminated 4/91 | ||
| PLM Remarketing Division of PLM, Inc. | PLEX | added 10/81; eliminated 7/90 | |
| PLM, Inc. | PLMX | added 1/78; 1/80; eliminated 7/84 | |
| Plymouth Short Line, Ltd. | PSLL | eliminated 1/92; 1/94-7/2000 | |
| PMA Transportation Corp. | PMAX | added 1/79; 1/80; eliminated 1/94; 7/2000 | |
| Pocono Northeast Ry., Inc. | PNER | added 10/82; eliminated 4/89; eliminated 1/91; 1/94 | |
| Point Comfort & Northern Ry. Co. | PCN | 1/75-1/80; added 4/80; 1/94-7/2000 | |
| Polar Supply, Inc. | AGKX | eliminated 4/80 | |
| AKGX | added 7/74; 1/75-1/80 | ||
| Poly Grinders Corp. | PGCX | added 7/77; 1/80; eliminated 7/81 | |
| Poly-America, Inc. | PAIX | added 1/91; 1/94; eliminated 4/94; 7/2000 | |
| Polymer Corp. Ltd. | PCLX | 1/52-10/66; eliminated 7/68 | |
| Polymont Plastics Corp. | PLIX | added 4/92; 1/94-7/2000 | |
| Polysar Inc. | PLIX | added 4/81; eliminated 4/92 | |
| Pook Valley Rail System | PVRX | Jul-00 | |
| Poole Chemical, Inc. | PCHX | 1/94-7/2000 | |
| Port Bienville R.R. | PBVR | added 10/81; 1/94; eliminated 4/98; 7/2000 | |
| Port Everglade Ry. | PER | 1/75-1/80 | |
| Port Huron and Detroit R.R. Co. | PH&D | 7/65-10/66 | |
| PHD | 1/75-7/2000 | ||
| Port Jersey | PJR | 1/75-7/2000 | |
| Port of Oakland Ry. | POAK | 1/80-7/2000 | |
| Port of Palm Beach District | PPBD | 1/75-1/80 | |
| Port of Tillamook Bay R.R. | POTB | added 7/79; 1/80-7/2000 | |
| Port Railroad, Inc. | PRI | added 7/94; eliminated 7/96 | |
| Port Royal R.R. | PRYL | 1/94-7/2000 | |
| Port Terminal R.R. Association | PTRA | Jul-00 | |
| Port Terminal R.R. of South Carolina | PTR | 1/94-7/2000 | |
| PTSC | added 7/84; eliminated 1/85 | ||
| Port Townsend R.R., Inc. | PTRR | 1/75-7/2000 | |
| Port Utilities | PUCC | 1/75-1/80 | |
| Portland & Western R.R., Inc. | PNWR | Jul-00 | |
| Portland Electric Power Co. | PEP | 4/38-1/52 | |
| Portland General Electric Co. | PGEX | added 1/79; 1/80-7/2000 | |
| Portland Terminal Co. | PTM | 10/57-4/70 | |
| PTM | 1/94; eliminated 10/97 | ||
| Portland Terminal Co. (Me.) | PTM | 1/75-1/80 | |
| Portland Terminal R.R. Co. (Ore.) | NPT | 1/75-7/2000 | |
| Portland Terminal R.R. Co. (Oregon) | PTRC | Jul-00 | |
| Portland Traction Co. | PRTD | added 10/89; eliminated 7/92; 1/94-7/2000 | |
| Portland Traction Co., Portland R.R. and Terminal Division | PRTD | 10/57-1/80; eliminated 10/89 | |
| Portsmouth Division, Detroit Steel Corp. | PSLX | 1/52-10/57; eliminated 1/59 | |
| Poseyville and Owensville R.R. Co., Inc. | POR | added 1/88; eliminated 4/92; 1/94 | |
| Potash Corp. of Saskatchewan, Inc. | KCMX | added 10/90; eliminated 1/91 | |
| Potomac Electric Power Co. | PEPX | added 1/75; 1/75-7/2000 | |
| Power Silicates, Inc. | POWX | added 7/88; 1/94; eliminated 1/98; 7/2000 | |
| PPG Canada, Inc. | SCLX | added 7/84; eliminated 10/84 | |
| PPG Canada, Inc., Industrial Chemicals | SCLX | added 10/84; 1/94; eliminated 1/97 | |
| PPG Industries, Inc. | PPGX | added 4/68; 4/70-7/2000 | |
| HOUX | 1/75-1/80 | ||
| SACX | added 4/68; 4/70; eliminated 10/72 | ||
| PQ Corp | PQX | added 4/78; 1/80; eliminated 4/80 | |
| PQCX | added 4/78; 1/80; eliminated 4/80; 7/2000 | ||
| Praire Coal Ltd. | PRCX | 1/94-7/2000 | |
| Prairie Central Ry. Co. | PACY | added 10/81; eliminated 1/86 | |
| Prairie Malt Ltd. | PMLX | added 4/97; 7/2000 | |
| Prairie Trunk Ry. | PARY | 1/80; added 4/80; eliminated 10/87 | |
| Praxair, Inc. | HYDX | added 1/93; 1/94-7/2000 | |
| LCIX | added 1/97; 7/2000 | ||
| LTCX | added 1/93; 1/94-7/2000 | ||
| UCOX | added 1/93; 1/94; eliminated 4/96; 7/2000 | ||
| Premier Equipment Leasing Co. | PELX | 1/94-7/2000 | |
| Prentiss Wabers Products Co. | PWPX | Jan-52 | |
| Prescott & Northwestern R.R. | P&NW | 4/38-10/66 | |
| Pressure Tank Car Co. | PGAX | 7/65-1/75; eliminated 1/79 | |
| Pressure Vessel Service, Inc. | PVSX | added 7/82; eliminated 1/90 | |
| Prest-O-Lite Co., Inc. | POLX | 1/52-4/61 | |
| Preway Inc. | PWX | added 7/56; 10/57-4/70; eliminated 10/70 | |
| PWPX | eliminated 7/56 | ||
| Prince Albert Refineries Ltd. | PALX | 10/57-4/61 | |
| Private Fuel Storage, LLC | PFSX | added 7/2001 | |
| Private Rail Ltd. | PRLX | 1/94-7/2000 | |
| Process Engineering Inc. | PEIX | 1/80; eliminated 7/80 | |
| Procor Ltd. | PROX | added 1/74; 1/75-7/2000 | |
| AGCX | added 4/90; 1/94-7/2000 | ||
| CGBX | added 7/82; 1/94 | ||
| DCLX | 1/80-1/94 | ||
| FFIX | added 1/74; 1/75-7/2000 | ||
| MPTX | added 1/74; 1/75-7/2000 | ||
| SHLX | added 1/98; 7/2000 | ||
| UNPX | added 1/74; 1/75-7/2000 | ||
| Producers & Refiners Corp. (Sinclair Refining Co.) | PARX | Apr-38 | |
| Productos Forestales, S.A. | PFSX | 1/52-7/65; eliminated 10/66 | |
| Products Tank Line (Union Tank Car Co.) | PX | Apr-38 | |
| Professional Lease Management, Inc. | PLMX | added 4/74; 1/75; eliminated 1/78 | |
| Proflame, Inc. | CGSX | added 1/79; 1/80-7/2000 | |
| Progress Rail Services Corp. | PRSX | added 7/98; 7/2000 | |
| KPXX | added 7/96; 7/2000 | ||
| KYRX | added 10/99; 7/2000 | ||
| LSMX | added 10/98; 7/2000 | ||
| SPSX | added 10/93; 1/94-7/2000 | ||
| Progress Rail Services Corp. d/b/a Sidney & Lowe R.R., Inc. | SLGG | added 4/97; 7/2000 | |
| Proleride Transport System, Inc. | PTSX | added 7/64; 7/65-4/70; eliminated 10/72 | |
| Prolerized Steel Corp. | PSCX | added 7/60; 4/61-10/66; eliminated 10/69 | |
| Propane Gas Service, Inc. | PGSX | 1/52-4/61 | |
| Protane Corp., Division of Northern Gas Co. | TGCX | added 10/68 | |
| Protane Corp., Division of Northern Propane Gas Co. | TGCX | 4/70; eliminated 10/74; 1/75-1/80 | |
| Protex Industries, Inc. | PDAX | 7/65-1/75; eliminated 4/78 | |
| Providence and Worcester Co. | PW | added 4/73; 1/75-1/80; eliminated 4/81 | |
| Providence and Worcester R.R. Co. | PW | added 4/81; 1/94-7/2000 | |
| WRWK | added 1/83; 1/94-7/2000 | ||
| PSI Energy, Inc. | PSIX | added 1/91; 1/94-7/2000 | |
| JEPX | added 1/99; 7/2000 | ||
| LERX | 7/2000; added 10/2000 | ||
| WRPX | added 1/91; 1/94; eliminated 10/98; 7/2000; added 10/2000; eliminated 1/2001 | ||
| PTO, Inc. | PTOX | added 4/86; 1/94-7/2000 | |
| PTS Inc. | PTXX | added 1/93; 1/94; eliminated 1/99; 7/2000 | |
| Public Service Co. of Colorado | PSCX | added 4/73; 1/75-1/80 | |
| HHHX | added 10/2000 | ||
| Public Service Co. of Indiana, Inc. | PSIX | 4/70; added 10/70; 1/75-1/80; eliminated 1/91 | |
| WRPX | added 10/78; 1/80; eliminated 1/91 | ||
| Public Service Co. of New Hampshire | PNHX | Jan-94 | |
| Public Service Co. of Northern Illinois | PSIX | Jan-52 | |
| Public Service Co. of Oklahoma | OPSX | added 1/79; 1/80-7/2000 | |
| Public Service Electric & Gas Co. | PSEX | Apr-38 | |
| Public Services Co. of Colorado | PSCX | 1/94-7/2000 | |
| Publicker Inc. | PUBX | Apr-38 | |
| Publicker Industries, Inc. | PIX | Jan-52 | |
| PUBX | added 1/80; 1/80; eliminated 7/90; 1/94-7/2000 | ||
| Publiker Industries, Inc. | THCX | added 1/86; 1/94; eliminated 10/94 | |
| Puget Sound Freight Lines | PSFL | 1/75-7/2000 | |
| Puget Sound Power & Light Co. | PSOX | added 1/70; 4/70-7/2000 | |
| Puget Sound Pulp & Timber Co. | PSTX | 1/52-4/61 | |
| Puget Sound Railway Historical Association, Inc. | PSHX | added 1/73; 1/75-1/80; eliminated 5/83 | |
| Puget Sound Tug & Barge | PSTB | 1/75-1/80 | |
| Pulaski Development Co. | LBWX | added 4/78; 1/80-1/94; eliminated 1/95 | |
| Pullman Leasing Co. | PLCX | added 4/81; eliminated 1/90 | |
| PLWX | added 4/81; eliminated 1/90 | ||
| PTLX | added 4/81; eliminated 1/90 | ||
| DSDX | added 4/81; eliminated 1/90 | ||
| TLCX | added 4/81; eliminated 1/90 | ||
| TLDX | added 4/81; eliminated 1/90 | ||
| WFIX | added 4/88; eliminated 1/90 | ||
| Pullman Leasing Co., a Subsidiary of Pullman Inc. | PLCX | 1/80; eliminated 4/81 | |
| PLWX | eliminated 1/90 | ||
| PTLX | 1/80; eliminated 4/81 | ||
| TLCX | 1/80; eliminated 4/81 | ||
| TLDX | 1/80; eliminated 4/81 | ||
| Pullman R.R. Co. | PLM | Apr-38 | |
| Pullman Transport Leasing Co., a Subsidiary of Pullman Inc. | PTLX | added 10/70; 1/75 | |
| DSDX | added 10/70; 1/75-1/80; eliminated 4/81 | ||
| TLCX | added 10/70; 1/75 | ||
| TLDX | added 10/70; 1/75 | ||
| Pure Carbonic Co., a Division of Air Reduction Co., Inc. (Shippers' Car Line Division of ACF Industries, Inc.) | PCIX | 10/66; eliminated 4/67 | |
| Purex Corp. | HBSX | Oct-57 | |
| Purex Corp., Ltd. | FELX | added 7/64; 7/65 | |
| FELX | 4/70; eliminated 10/70 | ||
| HBSX | Apr-61 | ||
| Putnam Tank Car Corp. | PNTX | 1/75-1/80; eliminated 1/82 | |
| Pyrofax Gas Corp. | PYFX | 7/65-1/80; eliminated 1/85 | |