4-6-6-4 4-6-6-4 construction roster 4-6-6-4 construction roster

| Railroad_quantity | Class_ | Road_numbers | Builder | Build_year |
|---|---|---|---|---|
| Northern Pacific Railway (47) | Z-8 | 5130–5149 | ALCO | 1943–1944 |
| Spokane, Portland and Seattle Railway (8) | Z-6 | 900–905 | ALCO | 1937 |
| Spokane, Portland and Seattle Railway (8) | Z-8 | 910–911 | ALCO | 1944 |
| Union Pacific Railroad (105) | CSA-1 | 3900–3914 | ALCO | 1936 |
| Union Pacific Railroad (105) | CSA-2 | 3915–3939 | ALCO | 1937 |
| Union Pacific Railroad (105) | 4664-3 | 3950–3969 | ALCO | 1942 |
| Union Pacific Railroad (105) | 4664-4 | 3975–3999 | ALCO | 1943 |
| Union Pacific Railroad (105) | 4664-5 | 3930–3949 | ALCO | 1944 |
| Western Maryland Railway (12) | M-2 | 1201–1212 | Baldwin | 1940–1941 |
| Western Pacific Railroad (7) | M-100 | 401–407 | ALCO | 1938 |