| 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 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 | 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 switchers | automatic train control | automobile |
| Autoracks | Auville WV | Auville Yard |
| Auxiliary Tender | auxiliary water tenders | Avondale Yard |
| Awards | Axle |
