Postcard photo of Reading 2-10-2 locomotive No. 3000, built ca. 1931.

(Union News Company, Public domain, via Wikimedia Commons)



Under the Whyte notation for the classification of steam locomotives, 2-10-2 represents the wheel arrangement of two leading wheels, ten powered and coupled driving wheels, and two trailing wheels. In the United States of America and elsewhere the 2-10-2 is known as the Santa Fe type, after the Atchison, Topeka and Santa Fe Railway that first used the type in 1903.


Schematic of the 2-10-2 steam locomotive wheel arrangement. Front of locomotive is on left.

(Gwernol, Public domain, via Wikimedia Commons)



The 2-10-2 wheel arrangement evolved in the United States from the 2-10-0 Decapod of the Atchison, Topeka and Santa Fe Railway (ATSF). Their existing 2-10-0 tandem compound locomotives, used as pushers up Raton Pass, encountered problems reversing back down the grade for their next assignments since they were unable to track around curves at speed in reverse and had to run very slowly to avoid derailing. Consequently, the ATSF added a trailing truck to the locomotives which allowed them to operate successfully in both directions. These first 2-10-2 locomotives became the forerunners to the entire 2-10-2 family.

The trailing truck allows a larger, deeper firebox than that of a 2-10-0. Like all ten-coupled designs, the long rigid wheelbase of the coupled wheels presented a problem on curves, requiring flangeless drivers, lateral motion devices and much sideplay on the outer axles. To limit this problem, the coupled wheels were generally small, up to 64 inches (1,630 mm) in diameter, which in turn generated the problem of insufficient counterweights to balance the weight of the driving rods.

The 2-10-2's inherent problem was the low speed restriction on the type, which was about 35 miles per hour (56 kph). Further, the 2-10-2 had other inherent restrictions. The massive cylinders that were required on locomotives in the United States for high tractive effort had the result that no reasonably sized valves could admit and exhaust steam at a sufficient rate to permit fast running. In addition the 2-10-2, like the 2-6-2, had its main rod connected to the middle coupled axle, very near to the centre of gravity, which created a violent nosing (waddling) action when operating at speed. The peak of the 2-10-2 design limitations was reached in the United States in 1926 and was overcome with the advent of the superior 2-10-4 design.


2-10-2 Tandem Compound Double-end "Decapod" Freight, Atchison, Topeka and Santa Fe, 1907.

(Howden, Boys' Book of Locomotives, 1907, Public domain, Wikipedia Commons)


Vauclain tandem compound cylinders, Atchison Topeka & Santa Fe Railroad. (Howden, Boys' Book of Locomotives, 1907, Public domain, Wikipedia Commons)


Locomotives with a 2-10-2 wheel arrangement were used in a number of countries around the world, including those in North America, Western Europe, China, the Soviet Union and Africa. Continental Europe saw a fair number of 2-10-2s, although the type was always less popular than 2-8-2 Mikados and 2-10-0 Decapods. A large number of European 2-10-2s were tank locomotives, taking advantage of the symmetrical nature of the wheel arrangement.


Baldwin Builders' Portrait of Santa Fe No. 3932, a 2-10-2 locomotive. (Baldwin Locomotive Works, Public domain, via Wikimedia Commons)

USRA Light Santa Fe 2-10-2. (1922 Locomotive Cyclopedia of American Practice, Public domain, Wikipedia Commons

United States

In the United States, the 2-10-2 type was produced between 1903 and 1930. The first were the Atchison, Topeka and Santa Fe Railway (AT&SF) engines of the 900 and 1600 series, which were an early type with few advantages over the 2-10-0 Decapod, save their ability to operate in reverse without derailing. By 1919, the AT&SF was building the definitive type, with the trailing truck supporting a large firebox. These were of the AT&SF 3800 class. One of them, AT&SF engine no. 3829, was equipped with an experimental two-axle trailing truck to become the first 2-10-4 Texas type.

About 2,200 Santa Fe types were built, including about 500 of the two United States Railroad Administration (USRA) First World War standard designs. There were two USRA standard 2-10-2s, the heavy version with an engine weight of 380,000 pounds (172,365 kg) and the light version with an engine weight of 352,000 pounds (159,665 kg). The Santa Fe had the most with 352 engines.

Of the 2-10-2’s built for the Santa Fe, only one has been preserved. AT&SF No. 940 is on static display outside the Santa Fe depot, now a Visitor Center, in Bartlesville, Oklahoma.

The heaviest 2-10-2s were ten locomotives built by Baldwin Locomotive Works for the Reading Railway c. 1931, weighing 451,000 pounds (204,570 kg), engine only.

At 104,000 pounds-force (460 kN), the Illinois Central Railroad's 2800 class rebuilds probably had the highest calculated tractive effort of any two-cylinder steam locomotive, although the adhesive weight was only 333,000 pounds (151,050 kg).

The Baltimore and Ohio Railroad ordered its first 2-10-2 from Baldwin in 1914. From 1914 to 1956, their 2-10-2s bore numbers commencing with 6, hence the nickname "Big Sixes". Designated the S class, there were several sub-classes. The first of the Big Sixes was retired in 1951 and were all scrapped by 1960.

The Southern Railway (SOU) ordered its first batches of fifty-five 2-10-2 Ss class steam locomotives (Nos. 5000-5054) from Baldwin in 1917. The second batches of twenty-five 2-10-2s (Nos. 6350-6374) were built by the American Locomotive Company's (ALCO) Richmond Works in 1918 originally for SOU's Cincinnati, New Orleans and Texas Pacific (CNO&TP) division. The latter batches were later moved to the SOU's main division and renumbered to 5055-5079 when they were proved to be too bulky for the CNO&TP tunnels' tight clearances. After receiving the last batches of Ss types, the SOU received fifty more 2-10-2s (Nos. 5200-5249) from ALCO's Brook Works in a USRA Light Santa Fe design which were classified as Ss-1. Both classes were assigned to SOU's Asheville division, banking and hauling heavy freight trains up the steep Saluda Grade and Old Fort Loops in the Blue Ridge Mountains. Between the late 1930s and the early 1950s, all of the Ss and Ss-1 steam locomotives were retired and scrapped with none surviving into preservation.

The Union Pacific Railroad rostered 144 2-10-2 locomotives, under the designation of TTT (Two-Ten-Two). They were divided into classes TTT-1 through TTT-7, but all had the same cylinder dimensions, driving wheel diameter and boiler pressure. Of these, only one locomotive survives; Union Pacific 5511 was donated to the Railroading Heritage of Midwest America, who plans to restore the locomotive to operating condition.


2-10-2 Freight Locomotive, Baltimore & Ohio Railroad, 1928. (Andy Dingley (scanner), Public domain, via Wikimedia Commons)

Southern Railway 2-10-2 No. 5016, 1916. (Internet Archive Book Images, CC0, via Wikimedia Commons)



In 1916, Canadian National Railways (CNR) took delivery of ten Class T-1-a 2-10-2s from an order made by the short-lived Canadian Government Railways and built by ALCO. Ten more were delivered from the Montreal Locomotive Works in 1918, and another 25 slightly modified T-1-cs in 1920 that were 500 kilograms (1,100 lb) lighter. Canadian Locomotive Company produced five T-2-as in 1924 (see photo below). Ten ALCO's named "T-3-a" were acquired from the Boston and Albany Railroad in 1928. Canadian Locomotive Company produced the last series of 2-10-2s for CNR, a batch of 15 T-4-as in 1929, and 18 T-4-bs in 1930.

The 2-10-2s began to be scrapped in the mid-1950s, with the last models being used until 1961. There are two surviving CNR 2-10-2 locomotives. One is No. 4008, on display at the CNR Station in Rainy River, Ontario, and the other is No. 4100, on display at the Canadian Railway Museum in Delson, Quebec.


No. 4103, a Canadian National Railway 2-10-2 Class T-2-a, built in 1924 by Canadian Locomotive Company.

(Postcard, W. Lenheim Collection)



Equivalent classifications
UIC class: 1E1, 1'E1'
French class: 151
Turkish class: 57
Swiss class: 5/7
Russian class: 1-5-1
First known tank engine version
First use: 1922
Country: Germany
Locomotive: Prussian T 20
Railway: Deutsche Reichsbahn
Designer: Prussian State Railways
Builder: Borsig & Hanomag
First known tender engine version
First use: 1903
Country: United States of America
Locomotive: AT&SF 900 class
Railway: Atchison, Topeka and Santa Fe
Builder: Atchison, Topeka and Santa Fe
Evolved from: 2-10-0, 2-8-2
Evolved to: 2-10-4
Benefits: Deeper firebox and better steaming than the 2-10-0
Drawbacks: Nosing action at speed
First known "True type" version
First use: 1919
Country: United States of America
Locomotive: AT&SF 3800 class
Railway: Atchison, Topeka and Santa Fe
Builder: Atchison, Topeka and Santa Fe
Evolved to: 2-10-4
Benefits: Larger and deeper firebox
Drawbacks: Nosing action at speed