Streamlined No. in front of a second non-streamlined K4s
William vu The most important express locomotive of the PRR from 1914 until it was replaced by diesel locomotives. It also survived all of its intended successors. Used the same boiler with Belpaire firebox as the L1s Mikado and influenced many other locomotives, including overseas. Number 3768 was fitted with a full streamlining by Raymond Loewy and others received partial fairing.