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 NotationCommon Name(s)Notes, First examples
0-2-2-0 The locomotives of the Mt. Washington Cog Railroad are examples of this type.
0-4-0Four-coupled 
0-4-2T  
0-4-4TForney four-coupled 
0-4-4-0  
0-4-6TForney four-coupled 
0-6-0Six-coupled 
0-6-2T Several examples were built by Baldwin (25896, 25953) for the Uintah Railroad.
0-6-2  
0-6-4TForney six-coupled 
0-6-6TForney six-coupled 
0-6-6-0 1904, Baltimore & Ohio. It was this first Mallet articulated built in the U.S.
0-8-0Eight-coupled 
0-8-2 Many examples of this type were 2-8-2's that had been modified for yard work.
0-8-8-0Angus1907: Erie; 1910: D&H; 1922: B&M, B&O, N&W, NYC
0-10-0Ten-coupled 
0-10-2UnionFive examples built in 1936 for the Union Railroad of Pittsburgh.
0-12-0T One example built in 1863 for the Philadelphia & Reading
2-2-0Planet 
2-2-2Single 
2-2-2-0Webb CompoundLondon & North Western Railway
2-2-2-2Webb CompoundLondon & North Western Railway
2-2-4T  
2-4-0Porter 
2-4-2ColumbianTwo 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.
2-4-4T  
2-4-4-0  
2-4-4-2  
2-4-6T  
2-6-0MogulFirst 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
2-6-2PrairieIn 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.
2-6-4Adriatic / Lionelnone in North America; very rare
2-6-4T Used in suburban service
2-6-6T  
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
2-6-6-6Allegheny1941: Chesapeake & Ohio
 Blue Ridge1945: 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.
2-8-0ConsolidationFirst 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.
2-8-2Mikado1897: built by Baldwin for export to Japan for the Japanese Government Railways. "Mikado" meant "Emperor of Japan".
 Mike 
 MacArthurWorld War II era name used to replace "Mikado".
2-8-4TBerkshire TankOne built 1904 by Baldwin for the Wellington & Manawatu Ry, New Zealand. Scrapped after merger into NZR because it was an orphan.
2-8-4Berkshire1925: 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.
 KanawhaChesapeake & Ohio
 LimaBoston & Maine, Illinois Central
2-8-8-0Bull Moose 
2-8-8-2Cab Forward1909: Southern Pacific (#4000), 1910: (#4002)
 Chesapeake1924: Chesapeake & Ohio
2-8-8-4Yellowstone1928: Northern Pacific
2-8-8-8-2Triplex1913: Erie (3 total), rear drivers under the tender
2-8-8-8-4Triplex1919: Virginian (1 example), rear drivers under tender
2-10-0DecapodFirst built in 1867 by Norris Brothers for the Lehigh Valley.
2-10-2Santa Fe1903: Atchison, Topeka & Santa Fe, built by ATSF & Baldwin.
 CentralIllinois Central
 DecapodSouthern Pacific
2-10-4Texas1925: Texas & Pacific, built by Lima.
 ColoradoChicago, Burlington & Quincy
 SelkirkCanadian Pacific
2-10-10-2 1911: Santa Fe (rebuilt from 2-10-2s); 1918: Virginian
4-2-0Six wheeler 
 Jervis1832: invented by John B. Jervis of the Mohawk & Hudson
4-2-2Bicycle 
4-2-4T inspection locomotives
4-4-0AmericanInvented by Henry Roe Campbell, patented 1836
 Eight wheeler 
4-4-2AtlanticTwo examples were built in 1887 and 1888. In 1895 this arrangement was used on the 70MPH express train of the Atlantic Coast Line.
 ChautauquaBrooks Locomotive Works
 MilwaukeeMilwaukee Hiawatha
4-4-4Reading1915: Reading
 JubileeCanadian Pacific
 Lady BaltimoreBaltimore & Ohio
4-4-4-4Baltimore&Ohio1937: Baltimore & Ohio #5600
 Duplex1942-45: 52 examples by the Pennsylvania Railroad
4-4-6Four-coupled, double-ender 
4-4-6-2 1909: Santa Fe (two examples)
4-4-6-4Duplex-Drive1944: 26 examples built by the Pennsylvania Railroad
4-6-0Ten wheelerFirst built in 1847 by the Norris Brothers for the Philadelphia and Reading Railroad.
4-6-2Pacific1901: 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.
4-6-4Hudson1927: New York Central & Hudson River Railroad. P. W. Kiefer of the NYC and ALCO were responsible for the design.
 MilwaukeeMilwaukee Road
 BalticMilwaukee Road
 Shore LineNew Haven
4-6-4-4Duplex-Drive1942: Pennsylvania Railroad (one example)
4-6-6T  
4-6-6-2Cab Forward1911: Southern Pacific
4-6-6-4Challenger1936: Union Pacific
4-8-0Twelve wheeler 
 Mastodon1882: Central Pacific (one example named Mastodon)
 JubileeWas a N&W 4-8-0 ever called a "Jubilee"???
4-8-2Mountain1907: New Zealand
1911: Chesapeake & Ohio. Used in the mountainous C&O territory.
 MohawkNew York Central
 New HavenNew Haven 3 cylinder
4-8-4 1921: Santa Fe
 Northern1926: Northern Pacific
 ConfederationCanadian National
 DixieNashville, Chattanooga & St. Louis (and other Southern Roads)
 Golden State / General ServiceSouthern Pacific
 GreenbrierChesapeake & Ohio
 MontanaGreat Northern???
 NiagaraNew York Central
 NiágaraNacionales de Mexico
 PoconoLackawanna
 PotomacWestern Maryland
 WyomingLehigh Valley
 Generals, GovernersRichmond, Fredericksburg & Potomac
4-8-8-2Cab Forward1928: Southern Pacific
4-8-8-4Big Boy1941: Union Pacific (25 examples)
4-10-0Mastodon1883: Central Pacific (only one example, named El Gobernador)
4-10-2Southern Pacific1925: Southern Pacific (#5000)
 Overland1925: UP (#8800)
4-12-2Union Pacific1926: UP (88 examples)
6-2-0Crampton1849: Camden & Amboy (three examples)
6-4-4-6Pennsylvania1939: 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+CJawn Henry1955: N&W (steam turbine electric)
2-truckShayGeared. 4-wheel trucks.
3-truckShayGeared. 4-wheel trucks.
4-truckShayGeared. 4-wheel trucks.
2-truckWillametteGeared. 4-wheel trucks.
3-truckWillametteGeared. 4-wheel trucks.
2-truckHeislerGeared. 4-wheel trucks.
3-truckHeislerGeared. 4-wheel trucks.
2-truckClimaxGeared. 4-wheel trucks.
3-truckClimaxGeared. 4-wheel trucks.

References
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 DruryGuide to North American Steam Locomotives1993, 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.