American Steam Locomotive Wheel Arrangements

North American steam locomotive are categorized by their wheel arrangement. The system used to categorize these wheel arrangements is called "The Whyte System". In this system numbers are assigned to the leading, driving, and trailing wheels of the locomotive. The first number is the number of leading wheels. The middle number (or numbers) give the number and arrangement of drivers. The last is the number of trailing wheels (typically under the firebox). For example a "2-8-4" or oOOOOoo means that there are two leading wheels (one axle), eight driving wheels (four axles), and 4 trailing wheels (two axles). A "T" at the end indicates that this is a tank engine (as opposed to a conventional tender engine).

This classification system got its name from Frederick Methvan Whyte who was a Dutch New York Central mechanical engineer. "Whyte" is the Dutch spelling of his name. You will often find his name spelled "F. M. White" (the anglo-saxon spelling) in railroad literature.

The system normally used to describe diesel-electric locomotives has also been used here for steam turbine electric locomotives. In this system, non-powered axles are given as numbers and powered axles are given as letters. There is no standard system of classification for geared locomotives such as Shays, Heislers and Climaxes. Instead, a brief description is given for each.

F.M.Whyte Notation Common Name(s) Notes, First examples
0-2-2-0   The locomotives of the Mt. Washington Cog Railroad are examples of this type.
0-4-0 Four-coupled  
0-4-4T Forney four-coupled  
0-4-6T Forney four-coupled  
0-6-0 Six-coupled  
0-6-2T   Several examples were built by Baldwin (25896, 25953) for the Uintah Railroad.
0-6-4T Forney six-coupled  
0-6-6T Forney six-coupled  
0-6-6-0   1904, Baltimore & Ohio. It was this first Mallet articulated built in the U.S.
0-8-0 Eight-coupled  
0-8-2   Many examples of this type were 2-8-2's that had been modified for yard work.
0-8-8-0 Angus 1907: Erie; 1910: D&H; 1922: B&M, B&O, N&W, NYC
0-10-0 Ten-coupled  
0-10-2 Union Five examples built in 1936 for the Union Railroad of Pittsburgh.
0-12-0T   One example built in 1863 for the Philadelphia & Reading
2-2-0 Planet  
2-2-2 Single  
2-2-2-0 Webb Compound London & North Western Railway
2-2-2-2 Webb Compound London & North Western Railway
2-4-0 Porter  
2-4-2 Columbian Two built in 1877 and six in 1878 by Rogers for New Zealand. First shown at the 1893 Columbian exposition in Chicago. "Columbia" is the poetical name for America.
2-6-0 Mogul First rigid frame: 1852; First swiveling frame: 1864 (L&N). Being the largest locomotive at the time, it was named after the Mohammedan Empire (India).
2-6-2T   1880s: Central Pacific; 1902: Central of New Jersey and Long Island Railroad
2-6-2 Prairie In 1885 six were built by Baldwin for New Zealand Railways. In 1898 Baldwin built a 2-6-2 (#4) for the McCloud River Railroad. In 1900 Brooks built this type for the Chicago, Burlington and Quincy to be used on the mid-western prairies.
2-6-4 Adriatic / Lionel none in North America; very rare
2-6-4T   Used in suburban service
2-6-6-0T   1905: New Zealand, one built, not successful
2-6-6-0   1909: Virginian
2-6-6-2T   Two examples built by Baldwin for the Uintah RR (#50, #51) in 1926-28 (later sold to Sumpter Valley) were the largest narrow gauge locomotives built for the USA.
2-6-6-2   1906: Great Northern; Last: 1949: C&O
2-6-6-4   1934: Pittsburg & West Virginia; Most powerful: Norfolk & Western 1936-50
2-6-6-6 Allegheny 1941: Chesapeake & Ohio
  Blue Ridge 1945: Virginian
2-6-8-0   The Southern and the Great Northern had the sole examples of this type. The Erie Railroad also briefly experimented with this type.
2-8-0 Consolidation First built by Baldwin in 1866 for the Lehigh Valley (which had recently been created by the merger of several smaller roads). Most popular wheel arrangement in U.S.
2-8-2 Mikado 1897: built by Baldwin for export to Japan for the Japanese Government Railways. "Mikado" meant "Emperor of Japan".
  MacArthur World War II era name used to replace "Mikado".
2-8-4T Berkshire Tank One built 1904 by Baldwin for the Wellington & Manawatu Ry, New Zealand. Scrapped after merger into NZR because it was an orphan.
2-8-4 Berkshire 1925: class A-1 demonstrator designed by W. E. Woodward of the Lima Locomotive works. Early tests were on the Boston & Albany which traveled the Berkshire Hills.
  Kanawha Chesapeake & Ohio
  Lima Boston & Maine, Illinois Central
2-8-8-0 Bull Moose  
2-8-8-2 Cab Forward 1909: Southern Pacific (#4000), 1910: (#4002)
  Chesapeake 1924: Chesapeake & Ohio
2-8-8-4 Yellowstone 1928: Northern Pacific
2-8-8-8-2 Triplex 1913: Erie (3 total), rear drivers under the tender
2-8-8-8-4 Triplex 1919: Virginian (1 example), rear drivers under tender
2-10-0 Decapod First built in 1867 by Norris Brothers for the Lehigh Valley.
2-10-2 Santa Fe 1903: Atchison, Topeka & Santa Fe, built by ATSF & Baldwin.
  Central Illinois Central
  Decapod Southern Pacific
2-10-4 Texas 1925: Texas & Pacific, built by Lima.
  Colorado Chicago, Burlington & Quincy
  Selkirk Canadian Pacific
2-10-10-2   1911: Santa Fe (rebuilt from 2-10-2s); 1918: Virginian
4-2-0 Six wheeler  
  Jervis 1832: invented by John B. Jervis of the Mohawk & Hudson
4-2-2 Bicycle  
4-2-4T   inspection locomotives
4-4-0 American Invented by Henry Roe Campbell, patented 1836
  Eight wheeler  
4-4-2 Atlantic Two examples were built in 1887 and 1888. In 1895 this arrangement was used on the 70MPH express train of the Atlantic Coast Line.
  Chautauqua Brooks Locomotive Works
  Milwaukee Milwaukee Hiawatha
4-4-4 Reading 1915: Reading
  Jubilee Canadian Pacific
  Lady Baltimore Baltimore & Ohio
4-4-4-4 Baltimore&Ohio 1937: Baltimore & Ohio #5600
  Duplex 1942-45: 52 examples by the Pennsylvania Railroad
4-4-6 Four-coupled, double-ender  
4-4-6-2   1909: Santa Fe (two examples)
4-4-6-4 Duplex-Drive 1944: 26 examples built by the Pennsylvania Railroad
4-6-0 Ten wheeler First built in 1847 by the Norris Brothers for the Philadelphia and Reading Railroad.
4-6-2 Pacific 1901: built by Baldwin for New Zealand Railways; 1902: Missouri Pacific & St. Louis, Iron Mountain & Southern
4-6-4T   Two converted in 1902 from 4-8-0s and 70 built in New Zealand 1910-1919. Canadian National Railways (6) and Central of New Jersey (6) had all American examples.
4-6-4 Hudson 1927: New York Central & Hudson River Railroad. P. W. Kiefer of the NYC and ALCO were responsible for the design.
  Milwaukee Milwaukee Road
  Baltic Milwaukee Road
  Shore Line New Haven
4-6-4-4 Duplex-Drive 1942: Pennsylvania Railroad (one example)
4-6-6-2 Cab Forward 1911: Southern Pacific
4-6-6-4 Challenger 1936: Union Pacific
4-8-0 Twelve wheeler  
  Mastodon 1882: Central Pacific (one example named Mastodon)
  Jubilee Was a N&W 4-8-0 ever called a "Jubilee"???
4-8-2 Mountain 1907: New Zealand
1911: Chesapeake & Ohio. Used in the mountainous C&O territory.
  Mohawk New York Central
  New Haven New Haven 3 cylinder
4-8-4   1921: Santa Fe
  Northern 1926: Northern Pacific
  Confederation Canadian National
  Dixie Nashville, Chattanooga & St. Louis (and other Southern Roads)
  Golden State / General Service Southern Pacific
  Greenbrier Chesapeake & Ohio
  Montana Great Northern???
  Niagara New York Central
  NiĆ”gara Nacionales de Mexico
  Pocono Lackawanna
  Potomac Western Maryland
  Wyoming Lehigh Valley
  Generals, Governers Richmond, Fredericksburg & Potomac
4-8-8-2 Cab Forward 1928: Southern Pacific
4-8-8-4 Big Boy 1941: Union Pacific (25 examples)
4-10-0 Mastodon 1883: Central Pacific (only one example, named El Gobernador)
4-10-2 Southern Pacific 1925: Southern Pacific (#5000)
  Overland 1925: UP (#8800)
4-12-2 Union Pacific 1926: UP (88 examples)
6-2-0 Crampton 1849: Camden & Amboy (three examples)
6-4-4-6 Pennsylvania 1939: Pennsylvania (one example: #6100)
6-8-6   1944: Pennsylvania (#6200 steam turbine, direct drive)
2+C+C+2   1938: UP (steam turbine electric, flash boiler)
2-C1+2-C1+B   1947: C&O (three examples, steam turbine electric)
C+C+C+C Jawn Henry 1955: N&W (steam turbine electric)
2-truck Shay Geared. 4-wheel trucks.
3-truck Shay Geared. 4-wheel trucks.
4-truck Shay Geared. 4-wheel trucks.
2-truck Willamette Geared. 4-wheel trucks.
3-truck Willamette Geared. 4-wheel trucks.
2-truck Heisler Geared. 4-wheel trucks.
3-truck Heisler Geared. 4-wheel trucks.
2-truck Climax Geared. 4-wheel trucks.
3-truck Climax Geared. 4-wheel trucks.

Abdill, George B. A Locomotive Engineer's Album. New York: Bonanza Books, 1965.
Alexander, Edwin P. Iron Horses: American Steam Locomotives, 1829-1900. New York: Bonanza Books, 1941.
Alexander, Edwin P. The Pennsylvania Railroad: A Pictorial History. New York: Bonanza Books, 1947.
Alexander, Edwin P. American Steam Locomotives: A Pictorial Record of Steam Power, 1900-1950. New York: Bonanza Books, 1950.
Comstock, Henry B. The Iron Horse. Galahad Press, 1971.
Holbrook, Stewart H. The Story of American Railroads. New York: Crown Publishers, 1947.
Keefe, Kevin P. ABC's of Railroading. Trains Magazine, May 1991.
MacBride, H. A. Trains Rolling. New York: MacMillan, 1953.
Morgan, David P. Steam's Finest Hour. Milwaukee: Kalmbach Books, 1959.
Morgan, David P. The Mohawk that Refused to Abdicate. Milwaukee: Kalmbach Books, 1975.
Locomotive & Railway Preservation Magazine    
Railroad Magazine    
Trains Magazine    
George Drury Guide to North American Steam Locomotives 1993, Kalmbach

This list was originally compiled by Richard Boylan. Since it's posting on May 30, 1991, on rec.railroad, Wes Barris has made many additions and modifications to it.