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Big Boy 4014

Short answer: Big Boy No. 4014 is one of 25 4-8-8-4 'Big Boy' articulated steam locomotives that the American Locomotive Company (ALCO) built for Union Pacific.

It was delivered in December 1941. Big Boys normally hauled freight between Ogden, Utah, and Cheyenne, Wyoming, across the Wasatch range. No. 4014 made its last revenue run in July 1959 and was retired in December 1961 after 1,031,205 miles. It was then displayed in Pomona, California, until Union Pacific reacquired it in 2013. After a restoration that included converting it from coal to oil, it returned to service in May 2019 and is now the world's largest operating steam locomotive. In 2026 it made a 14-state coast-to-coast America250 tour.

VideoWrite-up4 sources
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What should you know about Big Boy 4014?

Quick facts. Each one stands alone and has a stable ID you can cite.

  1. No. 4014 traveled 1,031,205 miles before retiring in 1961.

    DD-720-F01 · Write-up · Exhibit C (Retirement)

  2. It returned to service in May 2019 after Union Pacific converted it to burn oil.

    DD-720-F02 · Write-up · Exhibit D (Restoration)

Video transcript: Big Boy 4014: Union Pacific's 1941 Giant, Back Under Steam

DID YOU KNOW? The Union Pacific Big Boy No.4014 is the largest operational steam locomotive in the world, and one of only 25 Big Boy locomotives ever built for the Union Pacific Railroad. Constructed in 1941 by the American Locomotive Company, it was designed to haul immense freight trains over the steep grades of the Wasatch Mountains between Utah and Wyoming. The locomotive measures more than 132 feet long, weighs over 1.2 million pounds with its tender, and uses a 4-8-8-4 wheel arrangement that effectively combines two sets of driving wheels under a single boiler. NOW YOU KNOW!

Burned-in captions, read frame by frame (see transcript.md) · 30.1s Reel ·

Video coming soonBig Boy 4014 · Instagram Reel
Big Boy 4014: Union Pacific's 1941 Giant, Back Under Steam Instagram Reel · · 30.1s

The write-up

Union Pacific's 1941 giant, back under steam. The only one of eight surviving Big Boys that still runs.

  1. Exhibit A

    Built for the Wasatch

    Union Pacific had 25 Big Boys built, the first delivered in 1941, to haul heavy wartime freight, usually between Ogden, Utah, and Cheyenne, Wyoming. No. 4014 was delivered in December 1941.

  2. Exhibit B

    Hinged giant

    At about 133 feet long and 1.2 million pounds, Big Boys have articulated, or hinged, frames to get around curves. The 4-8-8-4 arrangement means four pilot wheels, two sets of eight drivers, each driven by its own engine, and four trailing wheels.

  3. Exhibit C

    Retirement

    No. 4014 made its last revenue run on July 21, 1959, and was retired on December 7, 1961, after 1,031,205 miles. It was then displayed at the RailGiants Train Museum in Pomona, California.

  4. Exhibit D

    Restoration

    Union Pacific reacquired it in 2013 and moved it to its Steam Shop in Cheyenne. The restoration included converting it from coal to No. 5 fuel oil, and the locomotive returned to service in May 2019 for the 150th anniversary of the transcontinental railroad.

  5. Exhibit E

    Still touring

    Of the eight Big Boys that survive, 4014 is the only one that runs. In 2026, Union Pacific sent it on a 14-state coast-to-coast America250 tour, from Sacramento on April 10 to Cheyenne on July 29.

Questions people ask about Big Boy 4014

How many Big Boys were built?

25, all for Union Pacific.

Source: Write-up · Exhibit A (Built for the Wasatch) · Union Pacific: Big Boy No. 4014; Union Pacific: Big Boy No. 4014 fact sheet (PDF)

What's the Big Boy's wheel arrangement?

4-8-8-4.

Source: Write-up · Exhibit A (Built for the Wasatch) · Union Pacific: Big Boy No. 4014; Union Pacific: Big Boy No. 4014 fact sheet (PDF)

When did 4014 return to service?

May 2019.

Source: Write-up · Exhibit B (Hinged giant) · Union Pacific: Big Boy No. 4014

Where was 4014 displayed before its restoration?

RailGiants Train Museum, Pomona.

Source: Write-up · Exhibit D (Restoration) · Union Pacific: Big Boy No. 4014; Wikipedia: Union Pacific 4014

What does the restored 4014 burn?

No. 5 fuel oil.

Source: Write-up · Exhibit E (Still touring) · Union Pacific: Big Boy No. 4014 fact sheet (PDF); Union Pacific: Big Boy No. 4014 2026 Coast-to-Coast Tour

Test Your Knowledge

All quizzes →

5 questions, all from this case file. Answers are revealed instantly.

  1. How many Big Boys were built?

    1. 8
    2. 25
    3. 100
    4. 4
    Show the answer

    Answer: B. 25 25, all for Union Pacific. Source: Write-up · Exhibit A (Built for the Wasatch) · Union Pacific: Big Boy No. 4014; Union Pacific: Big Boy No. 4014 fact sheet (PDF)

  2. What's the Big Boy's wheel arrangement?

    1. 4-6-6-4
    2. 2-8-2
    3. 4-8-8-4
    4. 4-4-0
    Show the answer

    Answer: C. 4-8-8-4 4-8-8-4. Source: Write-up · Exhibit A (Built for the Wasatch) · Union Pacific: Big Boy No. 4014; Union Pacific: Big Boy No. 4014 fact sheet (PDF)

  3. When did 4014 return to service?

    1. 1989
    2. 2009
    3. 2019
    4. 2025
    Show the answer

    Answer: C. 2019 May 2019. Source: Write-up · Exhibit B (Hinged giant) · Union Pacific: Big Boy No. 4014

  4. Where was 4014 displayed before its restoration?

    1. Pomona, California
    2. Omaha, Nebraska
    3. Denver, Colorado
    4. St. Louis, Missouri
    Show the answer

    Answer: A. Pomona, California RailGiants Train Museum, Pomona. Source: Write-up · Exhibit D (Restoration) · Union Pacific: Big Boy No. 4014; Wikipedia: Union Pacific 4014

  5. What does the restored 4014 burn?

    1. Coal
    2. Fuel oil
    3. Wood
    4. Electricity
    Show the answer

    Answer: B. Fuel oil No. 5 fuel oil. Source: Write-up · Exhibit E (Still touring) · Union Pacific: Big Boy No. 4014 fact sheet (PDF); Union Pacific: Big Boy No. 4014 2026 Coast-to-Coast Tour

Cite this case file

Easterling, Marcus. "Big Boy 4014." The Detail Department (DetailEnjoyer), case file DD-720, last updated May 31, 2026. https://detailenjoyer.com/case/big-boy-4014/

Permalink: https://detailenjoyer.com/case/big-boy-4014/ · Last updated

Markdown version

Cite a single fact by its ID, for example DD-720-F01 → https://detailenjoyer.com/case/big-boy-4014/#DD-720-F01