The K-4s class, ubiquitous in passenger service on the Pennsylvania Railroad, was a rugged one-size-fits-all machine. (The "s" in a PRR class designation indicates a superheated locomotive.) These Pacifics had 80-inch drivers and 27x28-inch cylinders, and carried 205 p.s.i. of boiler pressure. They weighed 308,900 pounds and exerted 44,460 pounds of tractive effort. However, their grate area was only 70 square feet, and they had 4041 square feet of evaporative heating surface and 943 square feet of superheater surface. Hence that they were often double-headed in order to keep heavy trains rolling at speed. No. 5492 appears here at the engine terminal in East St. Louis in September 1950, in a view by an anonymous photographer from the collection of my brother, David V. Leonard. She was the first of the final group of eight class K-4s Pacifics produced by the Juniata Shops in 1928.