4-4-0 is a locomotive type with a classification that uses the Whyte notation for the classification of steam locomotives by wheel arrangement and represents the arrangement: four leading wheels on two axles (usually in a leading bogie), four powered and coupled driving wheels on two axles, and a lack of trailing wheels. Due to the large number of the type that were produced and used in the United States, the 4-4-0 is most commonly known as the American type, but the type subsequently also became popular in the United Kingdom, where large numbers were produced.