Here the lone member of class S1a, No. 6000, reposes briefly in the yards of the Cincinnati Union Terminal in this photo from my brother David's collection. It was taken in September 1954, but the photographer is unknown. The class S Niagaras were intended for fast passenger service and were designed to accept 79-inch drivers for this purpose. However the first example, No. 6000, was delivered with 75-inch drivers because of a wartime restriction on building new passenger locomotives. She had 25x32-inch cylinders and a boiler pressure of 290 pounds. The 25 engines of the S1b class came shortly after the end of World War II and were built with the higher drivers. No. 6000 was so equipped, as shown here, in a subsequent shopping and her boiler pressure was reduced to 275 pounds to match that of the S1b class. She remained in service till 1956.

The other S1s had 25½x32-inch cylinders and developed a tractive effort of 61,570 pounds. Their trailing truck, which was not equipped with a booster engine, supported a firebox with 101 square feet of grate area. This, combined with an evaporative heating surface of 4,819 square feet and 1975 square feet of superheating surface, produced a maximum drawbar horsepower of 5070 at 62.5 miles per hour, the equivalent at the time of four diesel units. The total weight of locomotive and tender was 891,000 pounds.