Steam locomotives are classed by their wheel configurations. On steam locomotives the wheels that are driven by the steam engine are appropriately called drivers. Locomotives may also have sets of non-powered pilot wheels before and/or after the drivers.
Steam locomotives are classified using a system called "Whyte Notation". In Whyte notation 2-8-4 means that the locomotive has two pilot wheels in front of eight driving wheels, followed by four more trailing wheels. Note that this is... very different than the AAR Wheel Arrangement Notation used in classifying diesel and electric locomotives.
01 of 07
Steam Locomotive Class Names
Classes were frequently given names; a 2-8-4 locomotive was known as a "Berkshire". The Polar Express was pulled by a Berkshire locomotive.
Below are lists of steam locomotive class names, listed by their wheel configurations. If you've heard a locomotive referred to as a "Pacific" or a "Mogul" and want to know its wheel configuration, you can find it by using your browser's "Find in This Page" option, usually located in the Edit menu.
02 of 07
NotesWheel arrangements not listed were mostly less common types and their class names were usually alphanumeric codes which could vary from railroad to railroad. That is, if they were even used by more than one railroad.
On the Union Pacific, among other railroads, 4-8-4 locomotives were the "Northern" class. Railroads in the southern states wouldn't call a locomotive on their roster a "Northern". This resulted in many names for 4-8-4 locomotives. 4-8-4 class names are found in... their own section.
03 of 07
Single Axle Lead Pilot Truck Classes
- 2-2-2 (8ft Drivers): Great Western
- 2-2-2 (7ft Drivers): Star or Firefly
- 2-4-0: Hawthorn or Victoria
- 2-4-2: Columbia
- 2-6-0: Mogul
- 2-6-2: Prairie
- 2-8-0: Consolidation
- 2-8-2: Mikado or Calument (MacArthur after Pearl Harbor)
- 2-8-4: Berkshire (Kanawha on the Chesapeake and Ohio Railroad)
- 2-10-0: Decapod
- 2-10-2: Santa Fe
- 2-10-4: Texas
- 2-12-0: Centipede
04 of 07
Two Axle Lead Pilot Truck Classes
Continue to 5 of 7 below.
- 4-2-0: Jervis
- 4-2-2: Iron Duke/Rover
- 4-4-0: American
- 4-4-2: Atlantic
- 4-6-0: Ten Wheel
- 4-6-2: Pacific or St. Paul
- 4-6-4: Hudson or Baltic
- 4-8-0: Twelve Wheel
- 4-8-2: Mountain
- 4-8-4: *see 4-8-4 Locomotive Class Names (below)
- 4-10-0: Mastodon
- 4-10-2: Southern Pacific (named for the primary railroad to use them)
- 4-12-2: Union Pacific (named for the only railroad to use them)
05 of 07
4-8-4 Locomotive Class NamesAs railroads in southern states wouldn't use the name "Northern", many alternative names for the 4-8-4 were coined:
- Northern: Union Pacific and various other railroads
- Big Apple: Central of Georgia RR
- Confederation: Canadian National Railway
- Confederation: Grand Trunk Western RR
- Dixie: Nashville, Chattanooga & St. Louis Railway
- General, Governor, or Statesman: Richmond, Fredericksburg & Potomac RR
- Greenbrier: Chesapeake & Ohio Railway
- GS, Golden State or General Service:... Southern Pacific RR
- Niagara: New York Central RR
- Niagara:Ferrocarriles Nacionales de Mexico
- Pocono: Delaware, Lackawanna & Western RR
- Potomac: Western Maryland Railway
- Western: Denver & Rio Grande Western RR
- Wyoming: Lehigh Valley RR
06 of 07
Duplex Steam LocomotivesDuplex locomotives had two engines and two sets of drivers on a single rigid frame.
- 6-4-4-6: Pennsylvania (the only one made was owned by PRR)
07 of 07
Articulated Steam Locomotives
Articulated locomotives had multiple engines and sets of drivers that could move independently of each other.
- 2-6-6-6: Allegheny (C&O) or Blue Ridge (Virginian Railway)
- 2-8-8-0: Bull Moose
- 2-8-8-2: Y Class (Norfolk & Western)
- 2-8-8-4: Yellowstone
- 2-10-10-2: Virginian
- 4-6-6-4: Challenger
- 4-8-8-4: Big Boy
- 2-8-8-8-0: Triplex (1 made)
- 2-8-8-8-2: Triplex (3 made)
- 2-8-8-8-4: Triplex (1 made)
Edited by Ryan Kunkle