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Classes of Locomotives

Big Boy

The world's largest steam locomotive, twenty-five Big Boys were built exclusively for Union Pacific, the first of which was delivered in 1941. The locomotives were 132 feet long and weighed 1.2 million pounds. Because of their great length, the frames of the Big Boys were "hinged," or articulated, to allow them to negotiate curves. They had a 4-8-8-4 wheel arrangement, which meant they had four wheels on the leading set of "pilot" wheels which guided the engine, eight drivers, another set of eight drivers, and four wheels following which supported the rear of the locomotive. The massive engines normally operated between Ogden, Utah, and Cheyenne, Wyoming.

Although there are no Big Boys left in operation today, eight of them eventually were donated for public display in various cities around the country. They can be found in Pomona, California; St. Louis, Missouri; Dallas, Texas; Omaha, Nebraska; Denver, Colorado; Scranton, Pennsylvania; Green Bay, Wisconsin; and Cheyenne, Wyoming.


Union Pacific at one time owned 105 Challenger locomotives. Built between 1936 and 1943, the Challengers were nearly 122 feet long and weighed more than one million pounds. Articulated like their big brother, the Big Boy, the Challengers had a 4-6-6-4 wheel arrangement. They operated over most of the Union Pacific system, primarily in freight service, but a few were assigned to passenger trains operating through mountain territory to California and Oregon.

Today, one of two remaining Challengers, No. 3977, is on display in North Platte, Neb. The other, Challenger No. 3985, was kept by Union Pacific for excursion service.


The Northern class steam locomotives, with a wheel arrangement of 4-8-4, were used by most large U.S. railroads in dual passenger and freight service. Union Pacific operated 45 Northerns, built in three classes, which were delivered between 1937 and 1944. Initially the speedy locomotives, capable of exceeding 100 miles per hour, were assigned to passenger trains, including the famous Overland Limited, Portland Rose and Pacific Limited. In their later years, as diesels were assigned to the passenger trains, the Northerns were reassigned to freight service. They operated over most of UP's system.

The second series of Northerns was more than 114 feet long and weighed nearly 910,000 pounds. Most of them were equipped with distinctive smoke deflectors, sometimes called "elephant ears," on the front of the boiler. These were designed to help lift the smoke above the engine so the engine crew's visibility wasn't impaired when the train was drifting at light throttle.

The last steam locomotive built for Union Pacific was Northern No. 844. It was saved in 1960 for excursion and public relations service, an assignment that continues to this day. Any current excursions scheduled are posted on the Schedule page. Two other Northerns are on public display: No. 814 in Council Bluffs, Iowa and No. 833 in Ogden, Utah. A third Northern, No. 838, is stored in Cheyenne and is used as a parts source for No. 844.


The oldest locomotive owned by Union Pacific is 4-6-0 No. 1243. Built in 1890, it operated on various Nebraska branch lines until the 1930s, when it was transferred to Wyoming, where it operated on the Encampment Branch until it was retired in 1956. It was stored first in Rawlins, then Cheyenne, until it was cosmetically restored for public display in 1990. The refurbished locomotive was loaded on a special flat car and briefly toured with the steam excursion train. It then was moved to Omaha, and put on public display at the Western Heritage Museum in October 1996. It often is referred to as the "Harriman engine," since it's the only locomotive still owned by UP from the era when E.H. Harriman controlled the railroad.

Locomotives on Display

Union Pacific donated 46 steam locomotives of various types for display in museums and parks across the country. One steam locomotive, No. 844, was retained and never retired. It continues to run in special public relations service today.

A second locomotive, Challenger No. 3985, which had been on display in Cheyenne, Wyo., was restored to operating condition by a group of volunteer Union Pacific employees in 1981. It too, has been used in special excursion service since then.