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4-4-0, in the Whyte notation, denotes a steam locomotive with a wheel arrangement of four leading wheels on two axles (usually in a leading bogie), four powered and coupled driving wheels on two axles, and no trailing wheels.
First built in the 1830s, locomotives with this wheel arrangement were known as "standard" or "Eight-Wheeler" type. In the first half of the 19th century, almost every major railroad in North America owned and operated locomotives of this type, and many rebuilt their 4-2-0 and 2-4-0 locomotives as 4-4-0s.[1][2]
In April 1872, Railroad Gazette used "American" as the name of the type. The type subsequently also became popular in the United Kingdom, where large numbers were produced.[1]
The vast majority of 4-4-0 locomotives had tenders, though some tank locomotives (designated 4-4-0T) were built.