Southern Railway Ps-4 class

The Southern Railway Ps-4 was a class of 4-6-2 steam locomotives built for the Southern Railway (SOU), as well as its subsidiaries, the Alabama Great Southern (AGS) and the Cincinnati, New Orleans and Texas Pacific (CNO&TP). They were designed to pull SOU's heavy mainline passenger trains between Washington, D.C. and Atlanta, Georgia, including the CNO&TP trains between Cincinnati, Ohio and Jacksonville, Florida, as well as the AGS trains between Chattanooga, Tennessee and Meridian, Mississippi, via Birmingham, Alabama.

The first batch were built between 1923 and 1924 by American Locomotive Company's (ALCO) Schenectady Works in Schenectady, New York. These locomotives were originally painted black with gold linings and lettering until 1926, when they were all repainted in a brand-new Virginian green and gold paint scheme. This would include the next batch of Ps-4s, which were built at ALCO's Richmond Works in Richmond, Virginia, and signified as the First Ladies of the Pacifics around the SOU system. In 1928, the last batch of Ps-4s were built by Baldwin Locomotive Works (BLW) in Philadelphia, Pennsylvania.

In the 1940s, the Ps-4s were relegated to haul local mainline passenger trains and mail trains as their duties were taken over by SOU's new Electro-Motive Diesel (EMD) E6 diesel locomotives. Despite this, the Ps-4s were used in motive power pool service, where they were called in to pull the mainline passenger trains again whenever one of the diesel locomotives was unavailable. By 1949, their retirement began and all but one were scrapped in 1953. No. 1401 was spared from scrap and was donated to Smithsonian Institution, where it was put on permanent display at the National Museum of American History in Washington, D.C., around late 1961 as the sole survivor of the Southern Railway Ps-4 class, which have been regarded by Smithsonian curator John H. White Jr. as being "among the most celebrated passenger locomotives operated in the United States...."