UP 844 Climbing to Greenland Road UP 844 climbing a moderate grade between Castle Rock and Monument Colorado. This was the last steam engine delivered to the Union Pacific Railroad. It was initially used as a passenger hauler but was switched to freight service when diesel locomotives became available. It was initially coal-fired, but was changed to oil-firing. For a while it was renumbered 8444 but its designation was changed back to 844 when the conflicting engine was retired.