The Union Pacific 9000 class was the only class of steam locomotives with a 4-12-2 wheel arrangement ever to be built, also the 9000 class was the largest rigid frame locomotive ever built.

Feb 22, 2025 · The idea behind the 4-12-2 wheel arrangement began in May of 1925 when Union Pacific took delivery of its first 4-10-2, #8000. The locomotive was built by Alco, who was attempting to perfect three-cylinder steam technology believing it would offer more power.

The 4-12-2 was dubbed the 'Union Pacific' type and it namesake railroad was the only North American railroad to use it. The American Locomotive Company built eighty-eight of these fast freight locomotives for the Union Pacific Railroad.

The 4-10-2 locomotives were capable of slightly greater speed while being capable of pulling about 20% more tonnage. The Union Pacific wanted more and approached the American Locomotive Company about a design for a 4-12-2.

The Union Pacific Type steam locomotive is a non-articulated steam locomotive that featured a 4-12-2 wheel arrangement. Only 88 of these locomotives were built.

From the Collection of Denver Public Library Note: There are more photos of the UP 4-12-2's here. Enter "Union Pacific AND 9000", and increment the number for a new search.

A 4-12-2, in the Whyte notation for the classification of steam locomotives by wheel arrangement, is a locomotive with four leading wheels in a leading truck, twelve driving wheels (six axles) in a rigid frame, and two trailing wheels in a trailing truck.

The big 4-12-2 running on air back in February of 2022 running on 150 psi of shop air on short stretch of track laid in the shop...more.

4-2-2 Bicycle 4-2-4 6-2-0 Crampton 4 Drivers 0-4-0 Switcher 0-4-2 0-4-4/6 Forney

Jun 1, 2012 · A review of Lionel's newest 3-rail O-Scale Union Pacific 4-12-2 steam locomotive. Enjoy! More stuff at www.ericstrains.com.