The Ps-4 was Southern's premier class of Pacifics and also one of the most famous passenger steam locomotives in the United States. It was based on the USRA Heavy Pacific but had some adjustments such as smaller drivers, a shorter boiler and depending on the batch a Worthington or Elasco feedwater heater. Even with the driver diameter of 73 inches, they could pull 14 cars at 80 mph (129 km/h).
In two batches, a total of 44 Ps-4s were delivered to the Southern, twelve to the Cincinnati, New Orleans and Texas Pacific and eight to the Alabama Great Southern. The second batch locomotives were initially painted in a special Virginia Green and Gold livery following President Fairfax Harrison's visit to Great Britain. Today only number 1401 remains, which is not operational. 