Union Pacific 3985 is a four-cylinder articulated 4-6-6-4 "Challenger"-type steam locomotive built in July 1943 by the American Locomotive Company (ALCO) of Schenectady, New York, for the Union Pacific Railroad.

Union Pacific (UP) #3985 was one of 105 4-6-6-4 Challenger type locomotives owned and operated UP. Classified as a 4664-4 by the railroad, the locomotive was built by the American Locomotive Company in July 1943 with builder’s number 70174. It was included in the second order of the second version of Union Pacific’s 4-6-6-4 locomotives.

It is one of 105 Challengers built for Union Pacific between 1936 and 1943 and was, for many years, the only operating engine of its class in the world – the largest and most powerful operating steam locomotive. That title has transitioned to Big Boy …

Jan 6, 2023 · Union Pacific 3985, also known as the “Challenger”, is a four-cylinder simple articulated 4-6-6-4 “Challenger”-type steam locomotive built in July 1943 by the ALCO of Schenectady, New York, for the Union Pacific Railroad.

Feb 25, 2025 · Union Pacific 3985 is a 4-6-6-4 "Challenger"-type steam locomotive and the largest such locomotive still operating anywhere in the country. UP once owned more than one-hundred of these locomotives but today only two remain preserved.

Union Pacific Railroad No. 3985, also known as 'The Challenger', is a 4664-4 class 4-6-6-4 "Challenger" type articulated steam locomotive built by the American Locomotive Company (ALCO) in July 1943.

The Challenger No. 3985 was designed by Union Pacific and built in 1943 by the American Locomotive Company. It is one of 105 Challengers built for Union Pacific between 1936 and 1943 and is the only operating engine of its class in the world today – the largest and most powerful operating steam locomotive.

Union Pacific 3985 was built in 1943 by ALCo in Schenectady, New York. The locomotive was one of 105 articulated 4-6-6-4 Challenger-type locomotives produced for the Union Pacific.

Built by the American Locomotive Company (Alco) in 1943, UP #3985 features a 4-6-6-4 wheel arrangement, known as a Challenger type, and was one of 25 in this group of simple articulated Challengers delivered to Union Pacific.

UP "Challenger" 3985 was the world's largest operating steam locomotive until 4014 returned to service. It was built by American Locomotive Company (Alco) in July 1943 for the Union Pacific Railroad and 1 of 3 surviving locomotives in UP's steam fleet.