| 1 | A&BB | Akron & Barberton Belt R.R. | 7/1923-4/1938 | | NAKINA |
| 2 | A&BB | Akron & Barberton Belt R.R. | 7/23-4/38 | | NRHS |
| 3 | A&BB | AKRON & BARBERTON BELT RAILROAD | | | PWRC |
| 4 | A&BC | ALTOONA & BEECH CREEK RAILROAD | | | PWRC |
| 5 | A&E | ALTON AND EASTERN RAILROAD | | | PWRC |
| 6 | A&ER | ANNAPOLIS & ELK RIDGE RAILROAD | | | PWRC |
| 7 | A&GW | The Alberta & Great Waterways Ry. Co. (Northern Alberta Rys. Co.) | 7/1930-7/1936 | | NAKINA |
| 8 | A&GW | THE ALBERTA & GREAT WATERWAYS RY. CO. (NORTHERN ALBERTA RYS. CO.) | | | PWRC |
| 9 | A&K | ALLEGHANY AND KINZUA RAILROAD | | | PWRC |
| 10 | A&LM | Arkansas & Louisiana Missouri Ry. Co. (Huttig, Mansfield & Nacogdoches R.R.) | 7/1930 | | NAKINA |
| 11 | A&LM | Arkansas & Louisiana Missouri Ry. Co. | 7/1923 & 7/1932-7/1936 | | NAKINA |
| 12 | A&LM | The Arkansas & Louisiana Midland Ry. Co. | 8/1920 | | NAKINA |
| 13 | A&LM | Arkansas & Louisiana Missouri Ry. Co. | 23-Jul | | NRHS |
| 14 | A&LM | *THE ARKANSAS & LOUISIANA MIDLAND RY. CO. | | | PWRC |
| 15 | A&LM | *ARKANSAS & LOUISIANA MISSOURI RY. CO. {HUTTIG, MANSFIELD & NACOGDOCHES RAILROAD] | | | PWRC |
| 16 | A&M | Alabama & Mississippi R.R. Co. | 8/1920 | | NAKINA |
| 17 | A&M | ALABAMA & MISSISSIPPI RAILROAD CO. | | | PWRC |
| 18 | A&NE | ABBOTSFORD & NORTH EASTERN RR | | | PWRC |
| 19 | A&S | Missouri Pacific System | eliminated 1/1979 | | NAKINA |
| 20 | A&S | Abilene & Southern Ry. Co. | 8/1920-7/1954 | | NAKINA |
| 21 | A&S | Abilene & Southern Ry. Co. | 7/23-1/52 | | NRHS |
| 22 | A&S | Missouri Pacific System | eliminated 1/79 | | NRHS |
| 23 | A&S | ABILENE & SOUTHERN RY. CO. | | | PWRC |
| 24 | A&SA | Atlanta & St. Andrews Bay Ry. | 7/1923-1/1952 | | NAKINA |
| 25 | A&SA | Atlanta & St. Andrews Bay Ry. | 7/23-1/52 | | NRHS |
| 26 | A&SA | ATLANTA & ST. ANDREWS BAY RY. CO. | | | PWRC |
| 27 | A&SL | ADIRONDACK & ST LAWRENCE RR | | | PWRC |
| 28 | A&V | The Alabama and Vicksburg Ry. Co. | 7/1923 | | NAKINA |
| 29 | A&V | The Alabama and Vicksburg Ry. Co. (Illinois Central System) | 7/1930 | | NAKINA |
| 30 | A&V | The Alabama and Vicksburg Ry. Co. (Illinois Central R.R. Co.) | 7/1932 | | NAKINA |
| 31 | A&V | The Alabama and Vicksburg Ry. Co. | 23-Jul | | NRHS |
| 32 | A&V | ILLINOIS CENTRAL RR [ALABAMA & VICKSBURG RY. CO.} | | | PWRC |
| 33 | A&W | Alexandria & Western Ry. Co. | 8/1920-7/1923 | | NAKINA |
| 34 | A&W | Alexandria & Western Ry. Co. | 23-Jul | | NRHS |
| 35 | A&W | ALEXANDRIA & WESTERN RY. CO. | | | PWRC |
| 36 | A&WP | Atlanta & West Point R.R. Co. | 4/1938-10/1966 | | NAKINA |
| 37 | A&WP | Atlanta & West Point R.R. Co. | 4/38-10/66 | | NRHS |
| 38 | A&WP | ATLANTA & WEST POINT RAILROAD CO. | | | PWRC |
