Union Pacific No. 9000

Union Pacific No. 9000
No. 9000 on static display at the RailGiants Train Museum
Name	Union Pacific Type
Number(s)	9000 (Class numbered 9000–9087 among 88 total units)
Railway(s)	Union Pacific Railroad
Status	Non‑operating (static display)
Location	RailGiants Train Museum, Pomona, California
Technical specifications
Type	4-12-2 steam locomotive (“Union Pacific” type)
Designer(s)	American Locomotive Company (ALCO – multiple works)
Serial number(s)	66544
Manufacturer(s)	American Locomotive Company
Manufacturer(s)	Alco - Multiple Works
Build date	1926
Total produced	88 units total, built 1926–1930
Supplier of parts	UP Factory
Classification	9000
Wheel arrangement	4-12-2 “Union Pacific”
Axles	12
Dia. of Drivers	67 in (1,702 mm)
Weight	Locomotive: approximately 496,500 lb (225,209 kg) Tender (loaded): approximately 310,599 lb (140,886 kg) Combined: approximately 807,099 lb (366,095 kg)
Rail gauge	4 ft 8+1⁄2 in (1,435 mm) standard gauge
Valve gear	Gresley Conjugated (Three cylinder)
Cylinders	3 (two outside, one centered inside)
Boiler pressure	220 lbf/in2 (1.52 MPa)
Cylinder type	Outside cylinders: 27 in × 32 in (686 mm × 813 mm) Inside cylinder: 27 in × 31 in (686 mm × 787 mm)
Firegrate area	108.25 sq ft (10.06 m²)
Fuel type	Coal
Fuel capacity	Fuel capacity: ~42,000–44,000 lb (~19–20 t) Water capacity: ~18,000 US gal (~68,000 L)
Heating area	2,560 sq ft (238 m2)
Braking	Air Brakes (Cast Iron)
Performance figures
Maximum speed	50 mph (80 km/h)
Tractive effort	96,646 lbf (429.9 kN)
Factor of adhesion	3.66
Axle load	60,000 / 27,216
Service information
Running numbers	9000–9087 (class UP-1 through UP-5)
Name	Union Pacific Type
Liveries	Black/Silver
Disposition details
Retired	88
Preserved	One preserved (No. 9000), remainder scrapped
Disposition	Of 88 built, only No. 9000 survives; the rest were scrapped. Currently on static display at the RailGiants Museum, Pomona, CA
Number operational	0
Number scrapped	87

Union Pacific 9000 was the largest UP-1 class group of steam locomotive ever built with a 4-12-2 wheel arrangement, making it a unique chapter in American locomotive history. 9000 was built in 1926 by the American Locomotive Company (ALCO) for the Union Pacific Railroad. It holds the distinction of being the largest rigid-frame steam locomotives ever constructed. According to the Whyte system, this configuration consisted of four leading wheels, twelve driving wheels, and two trailing wheels. Because this Union Pacific locomotive was the sole operator of this design, the 9000 became informally known as the "Union Pacific type." 9000 was designed for heavy-duty service, this massive locomotive was built to haul both passenger and freight trains across the demanding terrain of the UP system, showcasing the railroad’s push for greater power and efficiency during the height of steam innovation.

The locomotive was retired in 1956, but instead of being scrapped, Union Pacific preserved it as a symbol of its bold innovations in steam technology. Today, Union Pacific No. 9000 is on static display at the RailGiants Train Museum at the Los Angeles County Fairgrounds in Pomona, California.

History (1926-1956)

Before the legendary No. 9000 was even conceived, Union Pacific experimented with a group of ten three-cylinder locomotives—the FTT-1 class 4-12-2s—delivered in 1925 and numbered #8000 and #8800–#8808. These early machines, though innovative, suffered from mechanical challenges and were not particularly successful.

Despite these issues, Union Pacific remained committed to the 4-12-2 concept and in 1926 placed an order for 15 new locomotives, to be built by the American Locomotive Company (ALCO). These were classified as the UP-1 class and numbered 9000–9014. A second batch of 15 units (9015–9029) followed in 1928, as Union Pacific doubled down on its investment in high-horsepower rigid-frame steam power.

No. 9000 was the very first of this improved class. Built jointly by UP and ALCO at a shared cost of $105,835.27, it was delivered to Union Pacific's shops in Omaha, Nebraska, on April 8, 1926. After final preparations, the locomotive was displayed outside the Omaha passenger depot on May 13.

The next day, May 14, 1926, No. 9000 departed west on its maiden voyage along the original Union Pacific mainline—part of the transcontinental route that had since been bypassed by newer alignments. Along the way, it was inspected at various division points before reaching Cheyenne, Wyoming, just after midnight on May 15.

Its first major test came May 16, 1926, when it tackled the steep grades of Sherman Hill—a key proving ground for heavy freight power. The event drew crowds, with curious onlookers lining U.S. Highway 30 to watch the enormous new locomotive in action. No. 9000 reached Laramie, Wyoming, after midnight and underwent full inspection and lubrication.

Throughout the next month, No. 9000 was extensively tested, logging over 4,159 miles during trials. These runs helped engineers evaluate its performance under real working conditions and allowed for adjustments to the design of future units.

Despite the UP-1’s power and potential, the locomotives still suffered from issues common to three-cylinder designs: difficulty maintaining the center cylinder and bearing, overheating of the main boxes, valve wear, and high back pressure at speed. These flaws, though serious, did not prevent Union Pacific from continuing the program—showing the railroad’s ambition to push the boundaries of steam technology.

Design

The most distinctive feature of the No. 9000 series was its three-cylinder design, with the center cylinder angled upward at about 8 degrees from horizontal. This angle wasn’t random—it was precisely calculated using Holcroft's cylinder and crank pin offset formula, which ensured the crank pin was also inclined at the same angle. This alignment helped synchronize the motion of all three cylinders, allowing the locomotive to deliver smoother power.

To prevent the center connecting rod from interfering with the first driving axle, Union Pacific engineers made a clever adjustment: they increased the spacing between the first and second driving axles. This extra room eliminated the need for a more complex (and less durable) clearance crank on the first axle.

Additionally, to help the massive rigid-frame locomotive handle curves, Alco installed lateral motion devices on the first and sixth driving axles. These allowed slight side-to-side movement of those axles, giving the long wheelbase greater flexibility when navigating tighter track geometry.

These design choices made the 9000s highly innovative for their time, blending brute strength with mechanical ingenuity to meet the demands of heavy mainline service.

Retirement to Preservation (1956-Present)

After completing its testing phase, No. 9000 was assigned to the Laramie roundhouse, where it served in the freight pool, maintained on a regular mileage-based schedule. It continued to operate reliably for three decades and was notably the last 4-12-2 of its class to remain in service, officially retired in May 1956.

In a fitting farewell, No. 9000 made its final journey under its own power, traveling to East Los Angeles Yard before being towed to its new home at the Los Angeles County Fairgrounds.

Today, Union Pacific 9000 rests in preservation at the RailGiants Train Museum in Pomona, California, under the care of the Southern California Chapter of the Railway & Locomotive Historical Society. While it remains a striking and historic exhibit, a return to operational status is considered highly unlikely, due to its size, mechanical complexity, and preservation priorities.

Trivia

• No. 9000 is the only surviving 4-12-2 steam locomotive in the world, making it a truly one-of-a-kind relic of steam history.
• It was one of 88 locomotives built in its class, and today it stands as the sole surviving example of this massive and unique wheel arrangement.
• The locomotive is occasionally charged with compressed air to about 150 PSI, allowing museum visitors to experience one of its signature features: blowing the iconic whistle.
• Union Pacific 9000 made a cinematic appearance in the film "UP: Last of the Giants," highlighting its legacy as a symbol of American steam power.

Gallery

9000 on display at Rail Giants

The 9000 appearing in the Kidsongs song The Locomotion.

No. 9000 on a train run to Pomona (in colour).

No. 9000 on a train run.

The engine photo'd for Lerro Productions.

9000 with UP No. 4014 prior to 4014's restoration to operating condition.

The engine in the turntable of a UP Roundhouse.

9000 new paint job

9000 on her way to Pomona for static display.

9000 air compressors and headlight

9000 twelve driving wheels

9000 being filmed in Last of the Giants.

9000 under the coal shoot.

9000 pulling a excursion train in early 1956

List of Members of the Union Pacific 9000 Class
UP-1 (Prototype):	9000 (Prototype)
UP-2:	9001 • 9002 • 9003 • 9004 • 9005 • 9006 • 9007 • 9008 • 9009 • 9010 • 9011 • 9012 • 9013 • 9014
UP-3 (Union Pacific):	9015 • 9016 • 9017 • 9018 • 9019 • 9020 • 9021 • 9022 • 9023 • 9024 • 9025 • 9026 • 9027 • 9028 • 9029
UP-3 (Oregon-Washington Railroad and Navigation Company):	9700 • 9701 • 9702 • 9703 • 9704 • 9705 • 9406 • 9707
UP-4:	9030 • 9031 • 9032 • 9033 • 9034 • 9035 • 9034 • 9035 • 9036 • 9037 • 9038 • 9039 • 9040 • 9041 • 9042 • 9043 • 9044 • 9045 • 9046 • 9047 • 9048 • 9049 • 9050 • 9051 • 9052 • 9053 • 9054
UP-5:	9063 • 9064 • 9065 • 9066 • 9067 • 9068 • 9069 • 9070 • 9071 • 9072 • 9073 • 9074 • 9075 • 9076 • 9077 • 9078 • 9079 • 9080 • 9081 • 9082 • 9083 • 9084 • 9085 • 9086 • 9087
UP-5 (Oregon Short Line):	9500 • 9501 • 9502 • 9503 • 9504 • 9505 • 9506 • 9507 • 9508 • 9509 • 9510 • 9511 • 9512 • 9513 • 9514
Fallen:	9001 • 9002 • 9003 • 9004 • 9005 • 9006 • 9007 • 9008 • 9009 • 9010 • 9011 • 9012 • 9013 • 9014 • 9015 • 9016 • 9017 • 9018 • 9019 • 9020 • 9021 • 9022 • 9023 • 9024 • 9025 • 9026 • 9027 • 9028 • 9029 • 9030 • 9031 • 9032 • 9033 • 9034 • 9035 • 9034 • 9035 • 9036 • 9037 • 9038 • 9039 • 9040 • 9041 • 9042 • 9043 • 9044 • 9045 • 9046 • 9047 • 9048 • 9049 • 9050 • 9051 • 9052 • 9053 • 9054 • 9063 • 9064 • 9065 • 9066 • 9067 • 9068 • 9069 • 9070 • 9071 • 9072 • 9073 • 9074 • 9075 • 9076 • 9077 • 9078 • 9079 • 9080 • 9081 • 9082 • 9083 • 9084 • 9085 • 9086 • 9087
Preserved:	9000 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