Union Pacific 3985

Union Pacific 3985 is a four-cylinder simple articulated 4-6-6-4 Challenger-type steam locomotive owned and operated by the Union Pacific Railroad. Built in July 1943 by the American Locomotive Company (ALCO) of Schenectady, New York, the 3985 is one of only two Union Pacific Challengers left in existence, along with No. 3977, which is on static display in North Platte, Nebraska.

Union Pacific 3985
Union Pacific Challenger No. 3985 running through Alton, Iowa on October 1, 2008
Type and origin
Power typeSteam
BuilderAmerican Locomotive Company (ALCO)
Serial number70174
Build dateJuly 1943
Rebuild date1979-1981
  UIC(2′C) C2′ h4
Gauge4 ft 8 12 in (1,435 mm) standard gauge
Driver dia.69 in (1,753 mm)
Wheelbase60 ft 4 12 in (18.402 m) Engine
121 ft 10 78 in (37.157 m) Engine + tender
Adhesive weight404,000 lb (183,000 kg; 183 t)
Loco weight627,900 lb (284,800 kg)
Tender weight446,000 lb (202,000 kg)
Total weight1,073,900 lb (487,100 kg)
Fuel typeNo. 5 fuel oil, originally Coal
Fuel capacity32 short tons (29 t; 29 long tons)
6,450 US gal (24,400 l; 5,370 imp gal)
Water cap25,000 US gal (95,000 l; 21,000 imp gal)
  Firegrate area
132 sq ft (12 m2) (grate removed in 1990)
Boiler94 in (2,400 mm)
Boiler pressure280 lbf/in2 (1.93 MPa)
Heating surface4,795 sq ft (445.5 m2)
  Tubes527 sq ft (49.0 m2)
  Flues3,687 sq ft (342.5 m2)
  Firebox140 sq ft (13 m2)
  Heating area2,162 sq ft (200.9 m2)
Cylinder size21 in × 32 in (533 mm × 813 mm)
Performance figures
Maximum speed70 mph (110 km/h)
Power output5,000 hp (3,700 kW)
Tractive effort97,350 lbf (433.03 kN)
Factor of adh.4.15
OperatorsUnion Pacific Railroad
Number in class11 of 25
  • UP 3985
  • UP 3967
  • UP 3718
  • CRR 676
First run1943
Last run1957
Current ownerUnion Pacific Railroad
DispositionPending 1472-day rebuild, based in Cheyenne, Wyoming, at the steam shop

The locomotive operated in revenue service until 1957. It was initially stored at the roundhouse in Cheyenne, Wyoming until 1975, when it was placed outdoors beside the Cheyenne depot. After a group of Union Pacific employees restored the locomotive to running condition in 1981, No. 3985 was placed into excursion service as part of the Union Pacific's heritage fleet and became the largest operational steam locomotive in the world, a title it would hold until the restoration of Union Pacific 4014 in May 2019. It remained in operation until mechanical problems took it offline in 2010, after which it was stored at the Union Pacific's Steam Shops in Cheyenne, Wyoming, pending a complete overhaul.


Designed by UP chief mechanical engineer Otto Jabelmann in 1941, UP 3985 was part of the second order of this second version of the Challenger. The design drew on recent experience with the enormous 4-8-8-4 Big Boy locomotives, and resulted in a locomotive in working order weighing some 317 short tons (288 t; 283 long tons) accompanied by a tender weighing 174 short tons (158 t; 155 long tons) when 2/3 loaded. Calculated tractive effort is 97,350 lbf (433.0 kN). The Challenger class was intended to speed up freight operations on the 0.82% grades across Wyoming; the 1.14% Wasatch Range climb east from Ogden was to be conquered by the Big Boys without helpers. The Challengers and Big Boys arrived on the scene just as traffic was surging in preparation for American participation in World War II.


Revenue service and retirement

UP 3985 was part of the 4664-4 group of Challengers built in 1943.[4] Although this group consisted of 31 locomotives, only 25 went to the Union Pacific. The other six were leased to the Denver and Rio Grande Western Railroad after completion, where they operated until the Rio Grande sold them to the Clinchfield Railroad in 1947.[5] While the Union Pacific Challengers operated primarily in freight service, a few were assigned to passenger trains.[6]

UP 3985 operated in its last "revenue" train service in 1957.[1] The locomotive was officially retired in 1962 and was stored in the Union Pacific's roundhouse at Cheyenne, Wyoming.[1] In 1975, it was brought out of storage and placed on an outdoor display beside the Cheyenne depot.[1]

Restoration and excursion career

Beginning in 1979, a group of Union Pacific employee-volunteers started work on restoring the locomotive, and it was returned to operational condition in 1981.[1] The locomotive made its first run during Railfair 1981, where it attended the opening of the California State Railroad Museum in Sacramento, along with Union Pacific 844, which had been in excursion service since 1960.[7] Originally built to burn coal, it was successfully converted to burn No. 5 fuel oil in 1990.[1]

In 1991, no. 3985 went to Railfair '91 along with 844 and DDA40X no. 6936 as well as towing UP 4-6-0 no. 1243 on a flatbed. The next year, the 3985 went to the National Railroad Historical Society's convention in San Jose, California. It participated in activities along with Southern Pacific 4-8-4 no. 4449 and SP 4-6-2 no. 2472.

The locomotive has pulled many excursion trains in three alternate identities during its career. In November 1992, No. 3985 was chosen to pull the Clinchfield Santa Train as Clinchfield Railroad No. 676, the number chosen as a continuation of the CRR's E-3 locomotives, which were numbered 670-675.[8] In May 1993, the locomotive masqueraded as sister engine No. 3967 as part of the 40th anniversary of the Rocky Mountain Railroad Club excursion, in which the original 3967, which was scrapped in 1960, pulled the same excursion on May 17, 1953.[9] During the same time period, the engine was renumbered again to 3718. No Challenger was ever assigned such a number, as the few 4664-4 locomotives that were converted to run on oil in 1945 were numbered 3708–3717.

Stationed at Cheyenne with other equipment in the UP's heritage collection, it was used for excursion trains and occasionally mainline freight on ferry moves. The most notable freight run of No. 3985 took place in 1990, in which American President Lines had a special request for the locomotive to pull a 143-car doublestack train between Cheyenne, Wyoming and North Platte, Nebraska.[10] It was in the maintenance shop at Cheyenne in 2007 and underwent necessary repairs for service in 2008.[11]

The locomotive was last used on the Missouri River Eagle Tour, which took place September 30 to October 14, 2010.[12] As part of the tour, No. 3985 was selected to pull the Ringling Brothers and Barnum & Bailey Circus train from Cheyenne to Denver, Colorado, where the circus held a special performance to celebrate P.T. Barnum's birthday.[12][13] Following the conclusion of the tour, it was taken out service for repairs and placed into storage, pending a 1472-day rebuild and 15-year inspection.[14][15]

In December 2018, Union Pacific requested from the Federal Railroad Administration (FRA) waivers to exempt UP Nos. 3985, 844 and 4014 from federal Positive Train Control (PTC) requirements;[15] in February 2019, the FRA officials responded that such waivers were not needed.[16]


  1. "Challenger No. 3985" (PDF) (Press release). Union Pacific. Archived from the original (PDF) on June 1, 2017. Retrieved May 6, 2019.
  2. Boehner, John (November 1982). "3985: The Engine, the People, the Restoration" (PDF). Trains. Kalmbach Publishing. pp. 32–38. Archived from the original (PDF) on May 19, 2019. Retrieved May 19, 2019.
  3. Drury 2015, p. 319.
  4. Solomon 2009, p. 70.
  5. Kalmbach, A.C., ed. (August 1944). "Almost Identical Twins". Trains Magazine. 4: 29.
  6. "Union Pacific 3985". American-Rails.com. Retrieved June 11, 2019.
  7. "Union Pacific Steam Program". American-Rails.com. Retrieved June 27, 2019.
  8. "Union Pacific's Clinchfield Challenge DVD". Pentrex. Archived from the original on June 5, 2017. Retrieved May 18, 2019.
  9. "Union Pacific's 40th Anniversary Steam Excursion DVD". Pentrex. Archived from the original on May 11, 2017. Retrieved June 14, 2019.
  10. "Heavy Freight and Union Pacific 3985". Pentrex. Archived from the original on July 17, 2019. Retrieved July 17, 2019.
  11. "Challenger No. 3985". Cheyenne Depot Museum. Archived from the original on August 14, 2016. Retrieved June 30, 2019.
  12. "Union Pacific Railroad's World's Largest Operating Steam Locomotive to Pull 'Ringling Bros.' Circus Train on Way to Sedalia, Mo., Celebration". Union Pacific. September 15, 2010. Archived from the original on August 19, 2014. Retrieved May 5, 2019.
  13. Shapiro, Mary (October 7, 2010). "Full steam ahead". St. Louis Post-Dispatch. Archived from the original on July 10, 2019. Retrieved July 10, 2019.
  14. Grant, Rich (May 5, 2016). "There's Only One Time to See Two "Big Boy" Locomotives at Cheyenne's Depot Days". HuffPost. Archived from the original on July 9, 2019. Retrieved July 9, 2019.
  15. "Big Boy 4014 gets drivers; UP asks for PTC waivers for three steam locomotives". Trains. December 13, 2018. Archived from the original on June 8, 2019. Retrieved June 9, 2019.
  16. Wrinn, Jim (February 28, 2019). "FRA: UP doesn't need waiver to run steam 11,000 miles in 2019". Trains. Archived from the original on June 9, 2019. Retrieved June 9, 2019.


  • Drury, George H. (2015). Guide to North American Steam Locomotives (2nd ed.). Kalmbach Publishing. ISBN 978-1-62700-259-2.
  • Solomon, Brian (2009). Alco Locomotives (1st ed.). Voyageur Press. ISBN 978-0-7603-3338-9.

Further reading

  • Botkin, William E.; Hill, Ronald G.; Kindig, R.H. (1985). Union Pacific 3985 (1st ed.). Collage. ISBN 978-0918654366.
  • Ehernberger, James L. (1993). Union Pacific Steam Challenger Portraits (1st ed.). Challenger Press. ASIN B000TXFDIC.
  • Kratville, William W. (1980). The Challenger Locomotives (1st ed.). Kratville Publications. ASIN B0006E9WN6.
  • Stagner, Lloyd E.; Reisdorff, James J. (2003). Fifty Years of Union Pacific Steam Excursions (1st ed.). South Platte Press. ISBN 978-0942035636.
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