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Union Pacific No. 3985

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Union Pacific Railroad No. 3985, famously known as "The Challenger" is a 4-6-6-4 articulated steam locomotive of the 4664-4 class. Built by the American Locomotive Company (ALCO) in July 1943, it served the Union Pacific Railroad (UP) extensively. From April 1981, No. 3985 operated as part of UP’s heritage excursion fleet, based in Cheyenne, Wyoming, until it was taken out of service indefinitely in October 2010. The locomotive was officially retired from excursion duty in January 2020. On April 28, 2022, ownership transferred to the Railroading Heritage of Midwest America (RRHMA) in Silvis, Illinois, where plans are underway to restore the Challenger to operational condition.

History

Design and Construction

Union Pacific No. 3985 was designed in 1943 by Otto Jabelmann, UP’s chief mechanical engineer, as part of a second series of 4-6-6-4 “Challenger” type locomotives. Drawing upon the design principles of the larger 4-8-8-4 “Big Boy,” the Challenger was engineered for fast, heavy freight service, especially over the 0.82% grades in Wyoming. While the Big Boys tackled the steeper 1.14% grades of the Wasatch Range, the Challengers offered improved performance on less demanding terrain. Weighing approximately 317 short tons (288 metric tons) in working order—with a two-thirds loaded tender weighing an additional 174 short tons (158 metric tons)—No. 3985 had a calculated tractive effort of 97,350 lbf (433.0 kN). These locomotives were built just in time to support the dramatic increase in rail traffic brought on by America’s entry into World War II

Revenue Service (1943 - 1957)

Documentary_on_Union_Pacific_3985.

Documentary on Union Pacific 3985.

Union_Pacific_3985_with_Maximum_Smoke_in_HD

Union Pacific 3985 with Maximum Smoke in HD

No. 3985 was delivered in 1943 as part of the 4664-4 class, which included 31 total units—25 of which went to the Union Pacific. The locomotive saw regular freight service until 1957, when it ran its final revenue train. It was officially retired from UP’s active roster in 1962. The following year, No. 3985 was cosmetically restored and featured at the 1963 National Railway Historical Society (NRHS) convention in Cheyenne, Wyoming, alongside fellow steam giants Big Boy No. 4023 and Northern No. 844. After the event, the locomotive was stored in the Cheyenne roundhouse along side with Big Boy No. 4023 before being placed on outdoor display near the Cheyenne depot in 1975.

Restoration and Excursion Career with UP (1981–2010)

A volunteer team of Union Pacific employees began restoring No. 3985 to operational condition in 1979. Their work culminated in March 1981, when the locomotive steamed again for the first time in decades. It made its public return during Railfair 1981 in Sacramento, California, appearing alongside No. 844.

To improve efficiency during long-distance runs, the locomotive was converted from coal to No. 5 fuel oil in 1990. While being converted to oil that year, Challenger 3977 was being used for parts because it was already an oil burner, so it's oil burner was put on 3985 for the conversion. That same year, No. 3985 famously hauled a 143-car doublestack container train between Cheyenne and North Platte, Nebraska, at the request of American President Lines—an extraordinary display of mainline steam power.

In 1991, No. 3985 attended Railfair 1991 with No. 844 and diesel DDA40X No. 6936. UP 4-6-0 No. 1243 also joined the trip, carried on a flatcar. The following year, 3985 traveled to the NRHS convention in San Jose, California, where it operated alongside Southern Pacific steamers No. 4449 and No. 2472.

One of 3985’s most unique moments came in November 1992, when it pulled the CSX Clinchfield Santa Train across Tennessee and Kentucky while disguised as Clinchfield No. 676. The following May, it again donned a new identity—first as No. 3967 to commemorate the 40th anniversary of a 1953 Rocky Mountain Railroad Club excursion. Later the next day, the 3985 would be renumbered again to 3718 because it was the last steam locomotive to be converted to oil and to nod the Challenger class locomotives that were converted and renumbered 3700-3717.

In July 1993, No. 3985 headed to the NRHS convention in Chicago, Illinois. On its way, it passed through flood-damaged territory in Missouri, including the Sedalia Subdivision, where it carefully traversed compromised track during the Great Flood of 1993. Before returning to Cheyenne, the locomotive was even pressed into freight service in Kansas City to help address a local power shortage.

In May 1994, it pulled a special train through California’s Cajon Pass accompanied by Union Pacific’s EMD E9 A-B-A diesel set. In 1999, No. 3985 double-headed with No. 844 en route to Railfair 1999. On the return journey, however, No. 3985 was forced to tow a disabled 844 after it suffered a boiler tube failure while on display.

Throughout its excursion career, No. 3985 remained based in Cheyenne, sharing the heritage shop with UP’s other historic equipment. The locomotive received regular maintenance through the 2000s, including repairs in 2007–2008.

Final Years and Second Retirement

In the fall of 2010, No. 3985 embarked on the Missouri River Eagle Tour—its final major excursion. A highlight of this tour was pulling the Ringling Brothers and Barnum & Bailey Circus train from Cheyenne to Denver, where a special performance celebrated P.T. Barnum’s birthday. On October 14, 2010, No. 3985 made its last official run for Union Pacific. Following this trip, the locomotive was removed from service and placed in storage pending repairs.

Eventually, Union Pacific officially retired 3985 from excursion service in January 2020, citing 3985's poor mechanical condition and that operating three steam locomotives was too much for the heritage fleet team as reasons; according to the Union Pacific Steam Team manager, Ed Dickens, said the team felt that maintaining three steam locomotives was too much for them to handle. No. 3985 also needed an extensive overhaul due to its poor mechanical condition as No. 4014 officially replaced No. 3985 in excursion service. Its tender has temporarily been repurposed for use behind 4014, due to 4014's original tender not being converted to oil-firing in time for the Big Boy's first excursion run.

Acquisition by RRHMA and Second Restoration (2022-present)

On April 28, 2022, Union Pacific announced the donation of steam locomotive No. 3985, 2-10-2 type 5511, DDA40X diesel locomotive 6936, and other heritage equipment to the Railroading Heritage of Midwest America (RRHMA) in Silvis, IL. RRHMA committed to restoring both 3985 and 5511 to operational condition. On May 13, RRHMA also agreed to return Big Boy No. 4014’s original tender to Union Pacific in exchange for 3985’s tender, to better prepare for 3985’s restoration. On November 11, 2022, No. 3985 was towed out of Cheyenne, Wyoming, and arrived at RRHMA’s Silvis facility—housed in the historic Rock Island Railroad shops—on November 19.

Dismantling and Early Restoration Work (2023)

On January 6, 2023, RRHMA began the initial phase of dismantling No. 3985. The cab was removed from the frame, and all major appliances were taken off the locomotive. The drawbars were disconnected and set aside in preparation for the future transfer of No. 4014’s original tender. With these steps complete, the team prepared to gut the boiler and begin work on removing the firebox sheets and stay bolts.[1]

In February 2023, RRHMA fully gutted No. 3985’s boiler, removing all internal piping. The air pumps, dynamo, lubricators, and injectors were also taken off for rebuilding. Work began on repairing the locomotive’s cylinders, while preparations were made for the next steps: performing a hammer test on the firebox and removing the fire trough, blower, burner, atomizer, and stoker—components that would be set aside for cleaning and refurbishment as part of the firebox restoration.[2]

In March 2023, RRHMA removed the fire trough, burner, and firebrick arch from No. 3985, tagging each component for sandblasting, pressure washing, and cleaning. The team also removed the steam pipes and disconnected the steam joints and turret valves at the front of the boiler. Upcoming tasks included removing the valve gear, marking boiler sheets for cutting, extracting the pistons and steam pipes, removing lubrication lines and safety valves for full boiler access, and disassembling the crossheads and crosshead guides to prepare the rods for sandblasting and inspection.[3]

In July 2023, RRHMA removed the safety valves, lubrication lines, and valve covers to access and extract the pistons, allowing the connecting rods to be disassembled for inspection and rebuild. The rear engine’s valve gear was also taken out and disassembled for cleaning. Meanwhile, the flue sheets were marked and fitted with lifting rings in preparation for removal and replacement. Inside the firebox, damaged sections of the inner sheets were identified and marked for removal, along with faulty stay bolts that were flagged for drilling and replacement using specifications from original Union Pacific drawings.[4]

In September 2023, RRHMA cut out the flue sheets and removed the damaged sections of No. 3985’s firebox. Work continued on drilling out defective stay bolts, which were being replaced with correct-spec replacements. Additional components removed included the compressors, air tanks, air piping, and the smokebox door. The steam and exhaust pipes were disassembled for cleaning and future replacement. Pistons were extracted from both engine units, along with valve components, crossheads, and crosshead guides to facilitate rod removal. The next major step was to tow 3985 to the drop pit to remove the wheelsets, which would be sent to Strasburg Rail Road for re-tiring.[5]

In October 2023, No. 3985 was moved outside by the newly restored DDA40X No.6936, where its exterior was blasted and primed. The air tanks were sent to the blast booth, thoroughly cleaned inside and out, and coated with enamel paint to protect against rust and contamination in the air system. Meanwhile, boiler plates were drilled, and hole locations were marked in preparation for stay bolt insulation and installation.[6]

In December 2023, RRHMA received a series of welcome holiday deliveries from Strasburg Rail Road, Steam Services of America, and a locomotive pipe manufacturer in Germany. The shipment included four truckloads of piping and six boxes filled with stay bolts, sleeves, and caps—all staged next to No. 3985 in preparation for installation in 2024. [7]

Major Restoration Milestones (2024)

In February 2024, RRHMA received newly fabricated superheaters from Steam Services of America and Strasburg Rail Road, all built to original Union Pacific specifications. No. 3985 underwent X-ray testing to assess the condition of the boiler material and to identify defective stay bolts requiring removal and replacement. The final flue sheet was removed, along with the smokestacks and smoke hoods, which were set aside for rebuilding. Next, the team will prepare the locomotive for installation of new firebox sheets and begin reconstructing and installing the cab deck ahead of full reassembly.[8]

In July 2024, all of No. 3985’s boiler and firebox sheets were milled and flanged, ready for installation. Rivets have been fabricated and are prepared for insertion into the smokebox during front sheet installation. Stay bolts were cut, and blanks were sent to contract shops to produce replacements for the incorrect materials installed in 2003 by Wasatch Contractors. Following X-ray inspections, bolts are being tested to determine which must be removed and replaced. The cab walls have been rebuilt with rotten planks removed, and the cab deck was shipped to Crawford Company, where it is being fabricated from solid diamond plate steel to replace the previously used deteriorated ties. The next steps include installing the new sheets, separating the boiler from the frame, and addressing steam pipe leaks and worn parts in the front engine unit. [9]

In August 2024, No. 3985 was prepared for stay bolt installation. The cab returned from the blast booth, with new decking ready for installation prior to painting. The boiler shell was grit blasted and needle scaled to remove rust and prepare for hammer testing and stay bolt replacement. The flange knuckle for the rear flue sheet was heat treated and fine-tuned, ready for drilling and installation into the boiler’s back head. The upcoming tasks include installing the sheets, replacing all stay bolts, and splitting the frame to access and work on the underside of the boiler.[10]

In September 2024, No. 3985 had its stay bolts installed in the boiler, and the first set of rivets was placed in the mud ring to prepare for the reinstallation of the flue sheets. Restoration work on the cab continued, focusing on installing new paneling and prepping the body for painting. The locomotive’s whistle was returned from Rizzoli Locomotive Works, having successfully passed steam and air tests, and is ready to be reinstalled during the upcoming hydrostatic test. The next major step is to split the frame and remove the front engine unit to repair the underside of the firebox and boiler up to the smokebox gooseneck, which developed a significant leak after being stored wet in the roundhouse. At this stage, the exhaust nozzles, T-pipe, and bearings will also be replaced as the rebuild advances to its next phase.[11]

In October 2024, the knuckle plates were pressed into shape, drilled, and prepared for installation in the boiler. RRHMA employed a laser cleaning system to remove rust from boiler sections requiring stay bolt replacement. All grease was stripped from No. 3985’s frame to ready it for washing and disassembly before towing the front engine unit to the blast booth. The front flue sheet was test-fitted and is set for installation once work resumes. Additionally, the cab’s stringers have all been replaced, with brace rods soon to be installed. Upcoming tasks include completing stay bolt installation, fitting repair patches, installing the flue sheets, and splitting the frame for sandblasting and parts replacement.[12]

In November 2024, the stay bolt replacement was completed, and the front sheet along with the combustion throat ring were prepared for installation. The rear sheet was cut from a blank and flanged, ready for drilling and the installation of superheater nozzles and the rear flange, which will secure the pipes to the boiler throat once the locomotive is reassembled and operational. Steel was also delivered for the base of the tank that will be installed in Big Boy’s tender before No. 3985 receives its own tender back. New scaffolding was constructed to provide better access to the boiler and to prepare No. 3985 for the installation of the cab deck and pedestal, allowing brake replacement work to commence. [13]

Restoration Progress into 2025

In February 2025, the front flue sheet was test-fitted, and holes were drilled to prepare for rivet installation. New crown bolts, delivered in January, are currently being installed. On the Big Boy tender, the brakes were replaced, and RRHMA continued the brake cylinder rebuild work originally begun by Ed Dickens in 2015. Over the coming months, the tank will be assembled, and once complete, the tenders of Big Boy and No. 3985 will be swapped.[14]

Between April and May 2025, RRHMA split the frame and removed the front engine unit from beneath the boiler—marking the first time this had been done on Challenger No. 3985 since the steam era around 1950. The whistle was restored and tested at Rizzoli Locomotive Works, and during an April shop tour, it was tested on Jeddo Coal Company No. 85 alongside No. 5511’s whistle. The next steps include laser-cutting rust from the front smokebox knuckle and smokebox, repairing a leak in the gooseneck, and reinstalling the flue sheets to prepare the boiler for a hydrostatic test scheduled for the fall.[15][16][17]

In June 2025, RRHMA began dismantling the appliances on the front engine unit frame to prepare it for cleaning in the blast booth prior to reassembly. Meanwhile, No. 3985’s boiler was prepped for the installation of the throat pipe and flue sheets. The final sets of stay bolts were delivered and are scheduled for installation once the rear and front flue sheets are fitted onto the throat pipe and welded into the boiler. Afterward, the remaining defective stay bolts will be removed and replaced. Upcoming tasks include installing the throat pipe and final stay bolts, rebuilding the front engine frame, installing a new steam pipe, replacing the gooseneck and centering device casting—similar to the replacement done on Big Boy—replacing the trucks and drivers, refurbishing the guide truck rockers, lowering No. 3985 back onto its frame, and conducting the hydrostatic test ahead of its anticipated first steam-up later this year or early next year.[18]

In July 2025, the new oil tank for the No. 3985 tender was delivered, Built of 1/4-inch plate steel by Dover Tank & Plate Company, the tank was fabricated in collaboration with welders experienced from the Pennsylvania Railroad T1 Trust’s No. 5550 project. The new tender oil tank has been completed and currently resides in Silvis, Illinois, awaiting installation. 4014's tender that is currently located at RRHMA-Silvis will be staying with UP #3985. The tender that is currently behind "Big Boy" #4014 will remain in Cheyenne. There are no plans for a tender swap. Both crews at RRHMA and the Union Pacific Steam Crew came to the mutual decision after hours of discussion from both parties, factoring in complex logistics and many other aspects regarding the swap. This will remain the plan moving forward with #3985's restoration.

In September 2025, No. 3985 underwent significant boiler work as part of its ongoing restoration by the Railroading Heritage of Midwest America (RHMA). One major milestone was the installation of the rear tube sheet, which was fitted and welded into place after extensive preparation and staybolt work on the firebox. Crews then shifted focus to the front tube sheet, a process involving several steps to ensure a proper steam tight seal. The sheet was heated and pulled against the boiler barrel to form its shape, rivet holes were prepared, and welding to the original boiler sheet followed. Final sealing will be completed through a process known as caulking, in which the edge of the sheet is forced into the barrel using an air hammer to ensure the boiler can withstand operating pressures of over 280 PSI.[19]

In October 2025, RRHMA fired up the forges and the final rivets were installed in No. 3985 completing the mud ring and the front tube sheet. The Cab Deck was test fitted and is now in final weld in preparation for reinstallation of the cab. RRHMA is down to the final 180 stay bolts in the rear sheet once they are installed sleeves and caps will be welded onto the ends to seal the boiler shell up for jacketing and the entire firebox and boiler will be sandblasted and sprayed with Apexior 1 primer inside the smoke box and boiler to prevent rust and to cover the stay bolts from combustion. Upcoming task is hydro where the locomotive will be subjected to 315 LBS of pressure, installing the pipes and superheaters, reinstalling the cab which will be covered in the next update, and final assembly where all the parts are put back on the locomotive in preparation for the steam test some time after the holidays.[20]

Trivia

  • In September 2010, 3985 was selected to pull the Ringling Brothers and Barnum & Bailey Circus Train from Cheyenne, WY to Denver, CO, where the circus held a special performance to celebrate P.T Barnum's birthday.
  • In November 1992, 3985 was chosen to pull the 50th Anniversary of the Clinchfield Santa Train on the CSX Transportation system in the Eastern United States. It was re-lettered and renumbered as Clinchfield Railroad No. 676. But it was her only outing on Eastern rails at the time because according to Steve Lee, not every railroad was built to accommodate the size of locomotives which were built in WWII, including the 3985 herself.
  • In 1989 and 1991, 3985 was temporarily fitted with an Illinois Central 3-chime whistle.
  • In 1991, 3985 went to the National Railroad Historical Society's convention in San Jose, CA.
  • In December 2018, Union Pacific requested from the Federal Railroad Administration (FRA) waivers to exempt 3985, 844, and 4014 from federal Positive Train Control (PTC) requirements. In February 2019, the FRA officials responded that such waivers were not needed, although 4014 was later successfully fitted with PTC technology in August 2021 before its big 2021 excursion tour and the UP is also still planning to eventually install PTC technology on 844 too.
  • 3985's tender is temporarily being used behind 4014 until its original tender is restored by the Railroading Heritage of Midwest America (RRHMA) in Silvis, IL, at which point, it will get its original tender back in exchange for 3985's tender.
  • In May 1993, 3985 hauled a passenger excursion to commemorate the 40th anniversary of the Rocky Mountain Railroad Club excursion. In addition, 3985 wore the additional smoke deflectors for the excursion and was also was renumbered to 3967, which pulled the original excursion in 1953, but later it was renumbered again - this time to 3718. (No Challengers were ever assigned the number 3718).
  • On May 17, 2003, for the 50th anniversary, 3985 hauled the Rocky Mountain Railroad Club excursion. It once again wore the additional smoke deflectors and was renumbered to 3967.
  • The locomotive appears in Last of the Giants from the late 1950s, Articulateds UP 3985 vs N&W 1218, and Union Pacific Streamliners and Classic Steam in excursion service.

Gallery

References

  1. ↑ https://www.trains.com/trn/news-reviews/news-wire/work-begins-on-union-pacific-challenger-no-3985/?fbclid=IwAR3ghVHRKN8h1B7j5QNB7stFYu_XYK-CT9JhmkFD95EELU9sn4ssVI1yZGI
  2. ↑ https://rrhma.com/2023-february-update/
  3. ↑ https://rrhma.com/2023-march-update/
  4. ↑ https://rrhma.com/july-2023/
  5. ↑ https://rrhma.com/2023-september-update/
  6. ↑ https://rrhma.com/2023-october-update/
  7. ↑ https://rrhma.com/2023-december-update/
  8. ↑ https://rrhma.com/2024-february-update/
  9. ↑ https://rrhma.com/july-2024-update/
  10. ↑ https://rrhma.com/2024-august/?fbclid=IwY2xjawEior1leHRuA2FlbQIxMQABHc9F7sMAk5f_q40fRKDqewBR2eaDM8oV8QewfX8c7UBqSXyvbbFAdFv0Dw_aem_vKk79IoljToxihNc7i1vFg
  11. ↑ https://rrhma.com/2024-september/?fbclid=IwY2xjawF05O1leHRuA2FlbQIxMQABHRa-ciu54r5GYXDiVT5Co8H-2U6vYaGGEzaldoXe4NWiYSOt0AObRsm45A_aem_ob6iJnZYXABaAqTwaAD0aw
  12. ↑ https://rrhma.com/2024-october/
  13. ↑ https://rrhma.com/2024-november/
  14. ↑ https://rrhma.com/2025-february/
  15. ↑ https://rrhma.com/3985-front-engine-removal-inside-look/
  16. ↑ https://rrhma.com/april-2025-update/
  17. ↑ https://rrhma.com/silvis-train-days-2025/
  18. ↑ https://rrhma.com/june-2025-update/
  19. ↑ https://rrhma.com/september-2025-update/
  20. ↑ https://rrhma.com/october-2025-update/

Union Pacific’s drawings

List of Union Pacific Challenger Locomotives
CSA-1: 3900 (3800) • 3901 (3801) • 3902 (3802) • 3903 (3803) • 3904 (3804) • 3805 • 3906 (3806) • 3807 • 3808 • 3909 (3809) • 3910 (3810) • 3911 (3811) • 3912 (3812) • 3913 (3813) • 3914 (3814)
CSA-2: 3815 • 3816 • 3817 • 3918 (3818) • 3819 • 3820 • 3821 • 3822 • 3823 • 3822 • 3823 • 3824 • 3825 • 3826 • 3827 • 3828 • 3829 • 3830 • 3831 • 3832 • 3833 • 3834 • 3835 • 3836 • 3837 • 3838 • 3839
4664-3: 3950 • 3951 • 3952 • 3953 • 3954 • 3955 • 3956 • 3957 • 3958 • 3959 • 3960 • 3961 • 3962 • 3963 • 3964 • 3965 • 3966 • 3967 • 3968 • 3969
4664-4: 3975 • 3976 • 3977 • 3978 • 3979 • 3980 • 3981 • 3982 • 3983 • 3984 • 3985 • 3986 • 3987 • 3988 • 3989 • 3990 • 3991 • 3992 • 3993 • 3994 • 3995 • 3996 • 3997 • 3998 • 3999
4664-5: 3730 • 3731 • 3732 • 3733 • 3734 • 3735 • 3736 • 3737 • 3738 • 3939 • 3740 • 3741 • 3742 • 3743 • 3744 • 3745 • 3746 • 3747 • 3748 • 3749
Clinchfield Railroad: Locomotive Type
Extinct: Fetter Challengers
Excursion Star: 3967 • 3985
Preserved: 3977 • 3985
Preserved Union Pacific Locomotives
UP Class 700 No. 737
UP Class C-2 No. 237 • No. 264 • No. 561 • No. 616 • No. 618 • No. 6051 • No. 6237
UP Class C-57 No. 407 • No. 421 • No. 428 • No. 437 • No. 460 • No. 477 • No. 480 • No. 481 • No. 485
UP Class MK-1 No. 2005
UP Class MK-7 No. 2537
UP Class MK-9 No. 2295
UP Class MK-10 No. 2564
UP Class T-57 No. 1242 • No. 1243
UP Class P-1 No. 3206
UP Class P-2 No. 3203
UP Class TTT-6 No. 5511
UP Class S-4 No. 4420
UP Class S-5 No. 4436 • No. 4439 • No. 4442
UP Class S-6 No. 4455 • No. 4466
UP Class FEF-1 No. 814
UP Class FEF-2 No. 833
UP Class FEF-3 No. 838 • No. 844
UP Class 9000 No. 9000
UP Heavy Challengers No. 3977 • No. 3985
UP Big Boys No. 4004 • No. 4005 • No. 4006 • No. 4012 • No. 4014 • No. 4017 • No. 4018 • No. 4023
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