| 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 | 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 |
