Union Pacific No. 844 belongs to the FEF-3 class of Northern-type steam locomotives.
Built by the American Locomotive Company in December 1944, No. 844 was the last steam locomotive delivered to Union Pacific. The FEF series was designed for fast passenger and freight work, using a 4-8-4 wheel arrangement. FEF-3 locomotives were the final and most advanced version of the series, with higher performance and improved operational capability.
No. 844 pulled famous Union Pacific trains including the Overland Limited, Los Angeles Limited, Portland Rose and Challenger. It was converted from coal to fuel oil in 1946 and later reassigned to fast freight service as diesel locomotives replaced steam on passenger routes.
Unlike the other FEF locomotives, No. 844 was never fully retired. After 1959 it was preserved for public-relations and excursion work, making it one of the best-known operating steam locomotives in North America. H-8, A3 and J class are different locomotive classes from other railways.