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 | Pictorial | Common Name(s) | Notes, First examples |
|---|---|---|---|
| 0-2-2 | Northumbrian | Stephenson's Rocket of 1829 | |
| 0-2-2-0 | The locomotives of the Mt. Washington Cog Railroad are examples of this type. | ||
| 0-4-0 | Four-coupled | ||
| 0-4-2T | Olomana | ||
| 0-4-4T | Forney four-coupled | ||
| 0-4-4-0 | |||
| 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. | ||
| 0-6-2 | Branchliner, Webb | ||
| 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 | Transfer | 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 | 12-coupled | One example built in 1863 for the Philadelphia & Reading | |
| 2-2-0 | Planet | ||
| 2-2-2 | Single, Jenny Lind, Patentee | ||
| 2-2-2-0 | Webb Compound | London & North Western Railway | |
| 2-2-2-2 | Webb Compound | London & North Western Railway | |
| 2-2-4T | Aerolite | ||
| 2-4-0 | Porter, Hanscom, Old English | ||
| 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. | |
| 2-4-4T | Forney, Mason Bogie | ||
| 2-4-4-0 | |||
| 2-4-4-2 | Little River | ||
| 2-4-6T | |||
| 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 | ||
| 2-6-6T | Mason Bogie | ||
| 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 / Mike | 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 | Huntington | Often used as inspection locomotives. Southern Pacific C.P. Huntington was an example of this wheel arrangement. | |
| 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, which was located in Chautauqua County, called these Chautauquas | ||
| 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 | Santa Fe | 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) | |
| 4-6-6T | |||
| 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 | ||
| Laurentian | Delaware & Hudson | ||
| Montana | Great Northern??? | ||
| Niagara | New York Central | ||
| Niagara | 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 | Willamette | Geared. 4-wheel trucks. | |
| Heisler | Geared. 4-wheel trucks. | ||
| Climax | Geared. 4-wheel trucks. | ||
| Shay | Geared. 4-wheel trucks. | ||
| 3-truck | Willamette | Geared. 4-wheel trucks. | |
| Heisler | Geared. 4-wheel trucks. | ||
| Climax | Geared. 4-wheel trucks. | ||
| Shay | Geared. 4-wheel trucks. | ||
| 4-truck | Shay | Geared. 4-wheel trucks. |