1914 K4S Blueprint Drawing Poster

The Pennsylvania Railroad's K4s 4-6-2 "Pacific" (425 built 1914–1928, PRR Altoona, Baldwin) was their premier passenger-hauling steam locomotive from 1914 through the end of steam on the PRR in 1957. Attempts were made to replace the K4s, including the K5 and the T1 duplex locomotive, but none was really successful, and the K4s hauled the vast majority of express passenger trains until replaced by diesel locomotives. The K4s was not powerful enough for the weight of trains it was often called upon to haul from the mid 1930s onward, and so they were often double or even triple headed. This was effective, but wasteful in that several crews were needed. The PRR did have the extra locomotives, because many had been displaced by electrification. Since the PRR had often referred to itself as the Standard Railroad of the World, the K4 has sometimes been referred to as the Standard Passenger Locomotive of the World.[citation needed]. The K4s is widely considered to be one of the greatest steam locomotives of all time. It is recognised as the State Steam Locomotive of Pennsylvania. On December 18, 1987, Pennsylvania Governor Robert P. Casey signed into law House Bill No. 1211 naming the PRR K4 as the “official” state locomotive, according that august title to both K4 survivors, 1361 and 3750.