Locomotive 3985 is a steam locomotive built by the Union Pacific Railroad in 1943. It is a 4-8-8-4 type locomotive, meaning it has four leading wheels, eight driving wheels, and another set of four trailing wheels. This design allows for greater stability and power, making it one of the largest steam locomotives ever built. After being retired in 1957, Locomotive 3985 was preserved and restored for public display and special excursions. It is notable for its impressive size and historical significance, representing the peak of steam locomotive technology during the mid-20th century.