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.
The Atchison, Topeka and Santa Fe Railway, often referred to as the Santa Fe or AT&SF, was one of the larger railroads in the United States. The railroad was chartered in February 1859 to serve the cities of Atchison and Topeka, Kansas, and Santa Fe, New Mexico. The railroad reached the Kansas–Colorado border in 1873 and Pueblo, Colorado, in 1876. To create a demand for its services, the railroad set up real estate offices and sold farmland from the land grants that it was awarded by Congress.
In 1948, 14 railroads in North America owned more than 1,000 steam locomotives each. See also: Historical sizes of railroads
