| A-end | A. H. Tabor | AAR |
| AB&C | Abandoned Tender | Abandonments |
| Abbott Road | Abilene VA | Abingdon |
| Abingdon Branch | Abingdon VA | AC&Y |
| AC-44C6M | Accidents | Accomodation |
| Accu-Flex paint | Accurail | Accurail's USRA hopper |
| ACF | Acquisitions | Ad |
| Adhesion | Advertising | AE Class |
| AFE | Agenda | Agents |
| AHM | air brake | Air Brakes |
| Air Conditioning | air hoses | Ajin |
| Ajin Precision Mfg | Akron Canto and Youngstown | Akron Canton & Youngston |
| Akron Canton & Youngstown | Akron OH | Albert G. Pendleton |
| Alberta VA | ALCO | ALCO C424 locomotive |
| ALCO C628 locomotive | Alco Model | ALCO PA locomotive |
| ALCO PA-2 locomotive | ALCO RS-3 locomotives | Alco RS-3\'s |
| ALCO RS11 locomotive | ALCO RSD12 locomotives | ALCO S-2 locomotive |
| ALCO T-6 | ALCO T-6 locomotives | Alcos |
| Alexander Kearney | Algren VA | Allegheny |
| Allfree-Hubbel cylinders | Alliance Machine Co. | Alligator |
| Alnwick Hill | Altavista VA | Alternative Designs |
| AM&O | Amateur | American Car & Foundry |
| American Coal Co. | American Lancer | American Model Builders |
| American Railroad Photography | American Viscose | AMTRAK |
| Andrew Dow | Andrews Trucks | Ann Arbor Railroad |
| Annual Report | anthracite | Appalachia |
| Applicance Failures | Appomattox Railroad | Appomattox River |
| Appomattox VA | ARA | Arcadia |
| Archeology | Architects | Architecture |
| Archival Data | Archives | Arcola VA |
| Argentine Kansas | Argentine Yard | Armored locomotive |
| Arnold | Arnold McKinnon | Arrow in Matoaka |
| ASAB | Ashland WV | Athearn |
| Athearn H-24-66 | Athearn Model | Athearn S-12 |
| Atlanta Birmingham & Coast RR | Atlantic | Atlantic Coast Line |
| Atlantic Mississippi & Ohio Railroad | Atlantic Mississippi and Ohio Railroad | Atlas |
| Atlas BK | audio | August A. Thieme |
| Austinburg | Austinville VA | Auto Carrier |
| automatic | Automatic Block Signals | Automatic Switcher |
| Automatic switchers | automatic train control | automobile |
| Autoracks | Auville WV | Auville Yard |
| Auxiliary Tender | auxiliary water tenders | Avondale Yard |
| Awards | Axle |
