American Locomotive Company
Union Pacific Big Boy
Union Pacific 4000
United States · 1941
1941 · Golden-age steam · Steam
Union Pacific Big Boy
Big Boy · 4000 class · 4014
Operational heritage · 4-8-8-4 · Whyte 4-8-8-4
Specification
| Class | Union Pacific 4000 |
|---|---|
| Nicknames | Big Boy, 4000 class, 4014 |
| Builder | American Locomotive Company |
| Year introduced | 1941 |
| Country built | United States |
| Region | United States |
| Operators | Union Pacific Railroad |
| Era | Golden-age steam |
| Motive power | Steam |
| Role | Freight |
| Whyte | 4-8-8-4 |
| UIC | (2′D)D2′ |
| Wheel arrangement | 4-8-8-4 |
| Gauge | 1,435 mm — standard gauge |
| Quantity built | 25 |
| Power | 6,290 drawbar horsepower, with indicated output higher |
| Tractive effort | 135,375 lbf |
| Top speed | 129 km/h · 80 mph |
| Weight | 772,250 lb engine; about 1,208,750 lb with tender |
| Length | 132 ft 9¼ in engine and tender |
| Status | Operational heritage |