St. Louis, Iron Mountain & Southern No. 5, a Porter 2-4-2. Built as a 2-4-2T, it was

later modified as a tender engine by the Crab Orchard and Egyptian Railway.

(Gary Lee Todd, Ph.D., CC0, via Wikimedia Commons)



Under the Whyte notation for the classification of steam locomotives, 2-4-2 represents the wheel arrangement of two leading wheels on one axle, four powered and coupled driving wheels on two axles and two trailing wheels on one axle. The type is sometimes named Columbia after a Baldwin 2-4-2 locomotive was showcased at the 1893 World's Columbian Exposition held at Chicago, Illinois.


Diagram of the 2-4-2 Wheel Arrangement. Front of locomotive on left.

(Gwernol, Public domain, via Wikimedia Commons)


Brief Notes

The wheel arrangement was widely used on passenger tank locomotives during the last three decades of the nineteenth and the first decade of the twentieth centuries. The vast majority of 2-4-2 locomotives were tank engines, designated 2-4-2T. The symmetrical wheel arrangement was well suited for a tank locomotive that is used to work in either direction.

When the leading and trailing wheels are in swiveling trucks, the equivalent UIC classification is 1'B1'.

While a number of 2-4-2 tender locomotives were built, larger tender locomotive types soon became dominant.



The tank-type 2-4-2T was common in the U.S. around the dawn of the twentieth century in both suburban passenger service and on logging railroads. The Baldwin Locomotive Works built a demonstrator tender type engine which was displayed at the Columbian Exposition of 1893. This led to the type's name. This locomotive featured ambitious seven foot tall driving wheels, and was one of the first tender-equipped locomotives with a trailing truck. This freed the firebox from having to sit narrowly between, or above, the drive wheels, and was a very influential design.

This inspired three major U.S. railroads (Atlantic Coast Line, Burlington and Reading) to purchase a few of the type. But the two-wheeled lead truck was never well-suited to high speed service on far-flung North American rails. Some were converted to 4-4-2 Atlantic types and others were converted to 4-6-0 Ten Wheelers. The display locomotive was donated to Columbia University. In one respect, however, it was a success. A great many Atlantic types would follow, most based on the design.


Model railroading

The Lionel Corporation used the 2-4-2 configuration in many of its O-27 locomotives. In the United States, this may be the most famous usage of a 2-4-2 configuration locomotive.



Equivalent classifications

  • UIC class 1B1, 1'B1'
  • French class 121
  • Turkish class 24
  • Swiss class 2/4
  • Russian class 1-2-1

First known tank engine version
First use: 1863
Country: United Kingdom
Locomotive: No. 21 White Raven
Railway: St Helens Railway
Designer: James Cross
Builder: Sutton Works
First known tender engine version
First use: 1877
Country: New Zealand
Locomotive: K class
Railway: New Zealand Railways
Builder: Rogers Locomotive Works