Northern Pacific Railway locomotives Mallet and Simple Articulated Locomotives Mallet and Simple Articulated Locomotives

| Class_ | Wheel_arrangement | Fleet_numbers | Manufacturer | Serial_numbers | Year_made | Quantity_made | Quantity_preserved |
|---|---|---|---|---|---|---|---|
| Z-6 | 4-6-6-4 | 5100–5120 | Alco | 68760–68780 | 1936–1937 | 21 | 0 |
| Z-7 | 4-6-6-4 | 5121–5126 | Alco | 69540–69545 | 1941 | 6 | 0 |
| Z-8 | 4-6-6-4 | 5130–5149 | Alco | 70143…71962 | 1943–44 | 20 | 0 |