4-8-4

4-8-4 (Northern)
Diagram of two small leading wheels, four large driving wheels joined by a coupling rod, and two small trailing wheels
Equivalent classifications
UIC class2′D2′
French class242
Turkish class48
Swiss class4/8
Russian class2-4-2
First known tender engine version
First use1926
CountryUnited States
LocomotiveNP class A
RailwayNorthern Pacific Railway
DesignerAmerican Locomotive Company
BuilderAmerican Locomotive Company
Evolved from4-8-2, 4-6-4
BenefitsDeeper firebox than the 4-8-2.

Under the Whyte notation for the classification of steam locomotives, 4-8-4 represents the wheel arrangement of four leading wheels on two axles, eight powered and coupled driving wheels on four axles and four trailing wheels on two axles. The type was first used by the Northern Pacific Railway, and initially named the Northern Pacific, but railfans and railroad employees have shortened the name since its introduction. It is most-commonly known as a Northern.