| Classification Symbol | Wheel Arrangement | Driving Wheel Diameter | Original Assigned Number Blocks |
| A | 4-4-0 | 63" or less | 100 — 199 |
| B | 4-4-0 | over 63" | 200 — 399 |
| C | 2-6-0 | 52"or less | 400 — 469 |
| D | 2-6-0 | 52" to 58" | 470 — 529 |
| E | 2-6-0 | over 58" | 530 — 999 |
| F | 4-6-0 | 52" or less | 1000 — 1015 |
| G | 4-6-0 | 52" to 58" | 1016 — 1199 |
| H | 4-6-0 | 58" to 63" | 1200 — 1499 |
| I | 4-6-0 | over 63" | 1500 — 1799 |
| J | 4-6-2 | 70" or less | 5000 — 5499 |
| K | 4-6-2 | over 70" | 5500 — 5999 |
| K | 4-6-4 | all | 5700 — 5999 (August 1930) |
| L | 2-8-0 | 52" or less | 1800 — 1804 |
| M | 2-8-0 | 52" to 58" | 1805 — 2200 |
| N | 2-8-0 | over 58" | 2201 — 2999 |
| O | 0-6-0 | all | 7000 — 7999 |
| P | 0-8-0 | all | 8000 — 8499 |
| Q | Oil-electric switchers | | 7700 — 7999 (May 1930) |
| R | 2-8-2 | 58" or less | 3000 — 3199 |
| S | 2-8-2 | over 58" | 3299 — 3999 |
| T | 2-10-2 | all | 4000 — 4999 |
| U | 4-8-2 | all | 6000 — 6999 |
| U | 4-8-4 | all | 6100 — 6999 (May 1927) |
| V | Oil-electric road locomotives | | 9000 — 9099 (October 1928) |
| W | 0-10-0 | all | 8500 — 8599 |
| X | Miscellaneous | all | 1 — 99 |
| Z | Straight electric locomotives | | 9000 -9999 |
